diff --git a/webapp/nodejs/src/app_handlers.ts b/webapp/nodejs/src/app_handlers.ts
index 4c5438ed..a4e4b089 100644
--- a/webapp/nodejs/src/app_handlers.ts
+++ b/webapp/nodejs/src/app_handlers.ts
@@ -26,6 +26,7 @@ import {
   FARE_PER_DISTANCE,
   getLatestRideStatus,
   INITIAL_FARE,
+  responseError,
 } from "./common.js";
 import type { CountResult } from "./types/util.js";
 import { requestPaymentGatewayPostPayment } from "./payment_gateway.js";
@@ -47,8 +48,11 @@ export const appPostUsers = async (ctx: Context<Environment>) => {
     reqJson.lastname === "" ||
     reqJson.date_of_birth === ""
   ) {
-    return ctx.text(
-      "required fields(username, firstname, lastname, date_of_birth) are empty",
+    return responseError(
+      ctx,
+      new Error(
+        "required fields(username, firstname, lastname, date_of_birth) are empty",
+      ),
       400,
     );
   }
@@ -86,7 +90,11 @@ export const appPostUsers = async (ctx: Context<Environment>) => {
         `INV_${reqJson.invitation_code}`,
       );
       if (coupons.length >= 3) {
-        return ctx.text("この招待コードは使用できません。", 400);
+        return responseError(
+          ctx,
+          new Error("この招待コードは使用できません。"),
+          400,
+        );
       }
 
       // ユーザーチェック
@@ -95,7 +103,11 @@ export const appPostUsers = async (ctx: Context<Environment>) => {
         [reqJson.invitation_code],
       );
       if (inviter.length === 0) {
-        return ctx.text("この招待コードは使用できません。", 400);
+        return responseError(
+          ctx,
+          new Error("この招待コードは使用できません。"),
+          400,
+        );
       }
 
       // 招待クーポン付与
@@ -124,14 +136,18 @@ export const appPostUsers = async (ctx: Context<Environment>) => {
     );
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
 export const appPostPaymentMethods = async (ctx: Context<Environment>) => {
   const reqJson = await ctx.req.json<{ token: string }>();
   if (reqJson.token === "") {
-    return ctx.text("token is required but was empty", 400);
+    return responseError(
+      ctx,
+      new Error("token is required but was empty"),
+      400,
+    );
   }
   const user = ctx.var.user;
   await ctx.var.dbConn.query(
@@ -220,7 +236,7 @@ export const appGetRides = async (ctx: Context<Environment>) => {
     );
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -230,8 +246,11 @@ export const appPostRides = async (ctx: Context<Environment>) => {
     destination_coordinate: Coordinate;
   }>();
   if (!reqJson.pickup_coordinate || !reqJson.destination_coordinate) {
-    return ctx.text(
-      "required fields(pickup_coordinate, destination_coordinate) are empty",
+    return responseError(
+      ctx,
+      new Error(
+        "required fields(pickup_coordinate, destination_coordinate) are empty",
+      ),
       400,
     );
   }
@@ -251,7 +270,7 @@ export const appPostRides = async (ctx: Context<Environment>) => {
       }
     }
     if (continuingRideCount > 0) {
-      return ctx.text("ride already exists", 409);
+      return responseError(ctx, new Error("ride already exists"), 409);
     }
     await ctx.var.dbConn.query(
       "INSERT INTO rides (id, user_id, pickup_latitude, pickup_longitude, destination_latitude, destination_longitude) VALUES (?, ?, ?, ?, ?, ?)",
@@ -336,7 +355,7 @@ export const appPostRides = async (ctx: Context<Environment>) => {
     );
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -346,8 +365,11 @@ export const appPostRidesEstimatedFare = async (ctx: Context<Environment>) => {
     destination_coordinate: Coordinate;
   }>();
   if (!reqJson.pickup_coordinate || !reqJson.destination_coordinate) {
-    return ctx.text(
-      "required fields(pickup_coordinate, destination_coordinate) are empty",
+    return responseError(
+      ctx,
+      new Error(
+        "required fields(pickup_coordinate, destination_coordinate) are empty",
+      ),
       400,
     );
   }
@@ -379,7 +401,7 @@ export const appPostRidesEstimatedFare = async (ctx: Context<Environment>) => {
     );
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -387,7 +409,11 @@ export const appPostRideEvaluatation = async (ctx: Context<Environment>) => {
   const rideId = ctx.req.param("ride_id");
   const reqJson = await ctx.req.json<{ evaluation: number }>();
   if (reqJson.evaluation < 1 || reqJson.evaluation > 5) {
-    return ctx.text("evaluation must be between 1 and 5", 400);
+    return responseError(
+      ctx,
+      new Error("evaluation must be between 1 and 5"),
+      400,
+    );
   }
   await ctx.var.dbConn.beginTransaction();
   try {
@@ -396,11 +422,11 @@ export const appPostRideEvaluatation = async (ctx: Context<Environment>) => {
       rideId,
     );
     if (!ride) {
-      return ctx.text("ride not found", 404);
+      return responseError(ctx, new Error("ride not found"), 404);
     }
     const status = await getLatestRideStatus(ctx.var.dbConn, ride.id);
     if (status !== "ARRIVED") {
-      return ctx.text("not arrived yet", 400);
+      return responseError(ctx, new Error("ride not arrived yet"), 400);
     }
 
     const [result] = await ctx.var.dbConn.query<ResultSetHeader>(
@@ -408,7 +434,7 @@ export const appPostRideEvaluatation = async (ctx: Context<Environment>) => {
       [reqJson.evaluation, rideId],
     );
     if (result.affectedRows === 0) {
-      return ctx.text("ride not found", 404);
+      return responseError(ctx, new Error("ride not found"), 404);
     }
 
     await ctx.var.dbConn.query(
@@ -421,14 +447,14 @@ export const appPostRideEvaluatation = async (ctx: Context<Environment>) => {
       rideId,
     );
     if (!ride) {
-      return ctx.text("ride not found", 404);
+      return responseError(ctx, new Error("ride not found"), 404);
     }
 
     const [[paymentToken]] = await ctx.var.dbConn.query<
       Array<PaymentToken & RowDataPacket>
     >("SELECT * FROM payment_tokens WHERE user_id = ?", [ride.user_id]);
     if (!paymentToken) {
-      return ctx.text("payment token not registered", 400);
+      return responseError(ctx, new Error("payment token not registered"), 400);
     }
     const fare = await calculateDiscountedFare(
       ctx.var.dbConn,
@@ -457,7 +483,7 @@ export const appPostRideEvaluatation = async (ctx: Context<Environment>) => {
       },
     );
     if (err instanceof ErroredUpstream) {
-      return ctx.text(`${err}`, 502);
+      return responseError(ctx, err, 502);
     }
     await ctx.var.dbConn.commit();
     return ctx.json(
@@ -466,9 +492,9 @@ export const appPostRideEvaluatation = async (ctx: Context<Environment>) => {
       },
       200,
     );
-  } catch (err) {
+  } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${err}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -571,7 +597,7 @@ export const appGetNotification = async (ctx: Context<Environment>) => {
     return ctx.json(response, 200);
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -631,23 +657,27 @@ export const appGetNearbyChairs = async (ctx: Context<Environment>) => {
   const lonStr = ctx.req.query("longitude");
   const distanceStr = ctx.req.query("distance");
   if (!latStr || !lonStr) {
-    return ctx.text("latitude and longitude is empty", 400);
+    return responseError(
+      ctx,
+      new Error("latitude and longitude is empty"),
+      400,
+    );
   }
 
   const lat = atoi(latStr);
   if (lat === false) {
-    return ctx.text("latitude is invalid", 400);
+    return responseError(ctx, new Error("latitude is invalid"), 400);
   }
   const lon = atoi(lonStr);
   if (lon === false) {
-    return ctx.text("longitude is invalid", 400);
+    return responseError(ctx, new Error("longitude is invalid"), 400);
   }
 
   let distance: number | false = 50;
   if (distanceStr) {
     distance = atoi(distanceStr);
     if (distance === false) {
-      return ctx.text("distance is invalid", 400);
+      return responseError(ctx, new Error("distance is invalid"), 400);
     }
   }
 
@@ -722,9 +752,9 @@ export const appGetNearbyChairs = async (ctx: Context<Environment>) => {
       },
       200,
     );
-  } catch (err) {
+  } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${err}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
diff --git a/webapp/nodejs/src/chair_handlers.ts b/webapp/nodejs/src/chair_handlers.ts
index c4de5d66..742b004b 100644
--- a/webapp/nodejs/src/chair_handlers.ts
+++ b/webapp/nodejs/src/chair_handlers.ts
@@ -2,7 +2,7 @@ import type { Context } from "hono";
 import { setCookie } from "hono/cookie";
 import type { RowDataPacket } from "mysql2";
 import { ulid } from "ulid";
-import { getLatestRideStatus } from "./common.js";
+import { getLatestRideStatus, responseError } from "./common.js";
 import type { Environment } from "./types/hono.js";
 import type {
   ChairLocation,
@@ -22,8 +22,11 @@ export const chairPostChairs = async (ctx: Context<Environment>) => {
   }>();
   const { name, model, chair_register_token } = reqJson;
   if (!name || !model || !chair_register_token) {
-    return ctx.text(
-      "some of required fields(name, model, chair_register_token) are empty",
+    return responseError(
+      ctx,
+      new Error(
+        "some of required fields(name, model, chair_register_token) are empty",
+      ),
       400,
     );
   }
@@ -32,7 +35,7 @@ export const chairPostChairs = async (ctx: Context<Environment>) => {
     [chair_register_token],
   );
   if (!owner) {
-    return ctx.text("invalid chair_register_token", 401);
+    return responseError(ctx, new Error("invalid chair_register_token"), 401);
   }
   const chairID = ulid();
   const accessToken = secureRandomStr(32);
@@ -55,7 +58,7 @@ export const chairPostActivity = async (ctx: Context<Environment>) => {
       chair.id,
     ]);
   } catch (e) {
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
   return ctx.body(null, 204);
 };
@@ -106,7 +109,7 @@ export const chairPostCoordinate = async (ctx: Context<Environment>) => {
     return ctx.json({ recorded_at: location.created_at.getTime() }, 200);
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -169,7 +172,7 @@ export const chairGetNotification = async (ctx: Context<Environment>) => {
     );
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
 
@@ -184,10 +187,10 @@ export const chairPostRideStatus = async (ctx: Context<Environment>) => {
       [rideID],
     );
     if (!ride) {
-      return ctx.text("ride not found", 404);
+      return responseError(ctx, new Error("ride not found"), 404);
     }
     if (ride.chair_id !== chair.id) {
-      return ctx.text("not assigned to this ride", 400);
+      return responseError(ctx, new Error("cnot assigned to this ride"), 400);
     }
     switch (reqJson.status) {
       // Acknowledge the ride
@@ -201,7 +204,11 @@ export const chairPostRideStatus = async (ctx: Context<Environment>) => {
       case "CARRYING": {
         const status = await getLatestRideStatus(ctx.var.dbConn, ride.id);
         if (status !== "PICKUP") {
-          return ctx.text("chair has not arrived yet", 400);
+          return responseError(
+            ctx,
+            new Error("chair has not arrived yet"),
+            400,
+          );
         }
         await ctx.var.dbConn.query(
           "INSERT INTO ride_statuses (id, ride_id, status) VALUES (?, ?, ?)",
@@ -210,12 +217,12 @@ export const chairPostRideStatus = async (ctx: Context<Environment>) => {
         break;
       }
       default:
-        return ctx.text("invalid status", 400);
+        return responseError(ctx, new Error("invalid status"), 400);
     }
     await ctx.var.dbConn.commit();
     return ctx.body(null, 204);
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };
diff --git a/webapp/nodejs/src/common.ts b/webapp/nodejs/src/common.ts
index 5daa62a9..6378bcd2 100644
--- a/webapp/nodejs/src/common.ts
+++ b/webapp/nodejs/src/common.ts
@@ -1,5 +1,7 @@
 import type { Connection, RowDataPacket } from "mysql2/promise";
 import type { Ride, RideStatus } from "./types/models.js";
+import type { Context } from "hono";
+import type { StatusCode } from "hono/utils/http-status";
 
 export const INITIAL_FARE = 500;
 export const FARE_PER_DISTANCE = 100;
@@ -59,3 +61,14 @@ export class ErroredUpstream extends Error {
     this.name = "ErroredUpstream";
   }
 }
+
+export const responseError = (
+  ctx: Context,
+  error: unknown,
+  statusCode: StatusCode,
+) => {
+  if (error instanceof Error) {
+    return ctx.json({ message: error.message }, statusCode);
+  }
+  throw new Error("error is not an instance of Error");
+};
diff --git a/webapp/nodejs/src/main.ts b/webapp/nodejs/src/main.ts
index 512629d4..29acf3e4 100644
--- a/webapp/nodejs/src/main.ts
+++ b/webapp/nodejs/src/main.ts
@@ -32,6 +32,7 @@ import type { Environment } from "./types/hono.js";
 import { execSync } from "node:child_process";
 import { internalGetMatching } from "./internal_handlers.js";
 import { createPool } from "mysql2/promise";
+import { responseError } from "./common.js";
 
 const pool = createPool({
   host: process.env.ISUCON_DB_HOST || "127.0.0.1",
@@ -110,7 +111,7 @@ async function postInitialize(ctx: Context<Environment>) {
   try {
     execSync("../sql/init.sh", { stdio: "inherit" });
   } catch (error) {
-    return ctx.text(`Failed to initialize\n${error}`, 500);
+    return responseError(ctx, error, 500);
   }
   try {
     await ctx.var.dbConn.query(
@@ -118,7 +119,7 @@ async function postInitialize(ctx: Context<Environment>) {
       [body.payment_server],
     );
   } catch (error) {
-    return ctx.text(`Internal Server Error\n${error}`, 500);
+    return responseError(ctx, error, 500);
   }
   return ctx.json({ language: "node" });
 }
diff --git a/webapp/nodejs/src/middlewares.ts b/webapp/nodejs/src/middlewares.ts
index 77135dab..428c096b 100644
--- a/webapp/nodejs/src/middlewares.ts
+++ b/webapp/nodejs/src/middlewares.ts
@@ -3,12 +3,17 @@ import { createMiddleware } from "hono/factory";
 import type { RowDataPacket } from "mysql2/promise";
 import type { Environment } from "./types/hono.js";
 import type { Chair, Owner, User } from "./types/models.js";
+import { responseError } from "./common.js";
 
 export const appAuthMiddleware = createMiddleware<Environment>(
   async (ctx, next) => {
     const accessToken = getCookie(ctx, "app_session");
     if (!accessToken) {
-      return ctx.text("app_session cookie is required", 401);
+      return responseError(
+        ctx,
+        new Error("app_session cookie is required"),
+        401,
+      );
     }
     try {
       const [[user]] = await ctx.var.dbConn.query<Array<User & RowDataPacket>>(
@@ -16,11 +21,11 @@ export const appAuthMiddleware = createMiddleware<Environment>(
         [accessToken],
       );
       if (!user) {
-        return ctx.text("invalid access token", 401);
+        return responseError(ctx, new Error("invalid access token"), 401);
       }
       ctx.set("user", user);
     } catch (error) {
-      return ctx.text(`Internal Server Error\n${error}`, 500);
+      return responseError(ctx, error, 500);
     }
     await next();
   },
@@ -30,18 +35,22 @@ export const ownerAuthMiddleware = createMiddleware<Environment>(
   async (ctx, next) => {
     const accessToken = getCookie(ctx, "owner_session");
     if (!accessToken) {
-      return ctx.text("owner_session cookie is required", 401);
+      return responseError(
+        ctx,
+        new Error("owner_session cookie is required"),
+        401,
+      );
     }
     try {
       const [[owner]] = await ctx.var.dbConn.query<
         Array<Owner & RowDataPacket>
       >("SELECT * FROM owners WHERE access_token = ?", [accessToken]);
       if (!owner) {
-        return ctx.text("invalid access token", 401);
+        return responseError(ctx, new Error("invalid access token"), 401);
       }
       ctx.set("owner", owner);
     } catch (error) {
-      return ctx.text(`Internal Server Error\n${error}`, 500);
+      return responseError(ctx, error, 500);
     }
     await next();
   },
@@ -51,18 +60,22 @@ export const chairAuthMiddleware = createMiddleware<Environment>(
   async (ctx, next) => {
     const accessToken = getCookie(ctx, "chair_session");
     if (!accessToken) {
-      return ctx.text("chair_session cookie is required", 401);
+      return responseError(
+        ctx,
+        new Error("chair_session cookie is required"),
+        401,
+      );
     }
     try {
       const [[chair]] = await ctx.var.dbConn.query<
         Array<Chair & RowDataPacket>
       >("SELECT * FROM chairs WHERE access_token = ?", [accessToken]);
       if (!chair) {
-        return ctx.text("invalid access token", 401);
+        return responseError(ctx, new Error("invalid access token"), 401);
       }
       ctx.set("chair", chair);
     } catch (error) {
-      return ctx.text(`Internal Server Error\n${error}`, 500);
+      return responseError(ctx, error, 500);
     }
     await next();
   },
diff --git a/webapp/nodejs/src/owner_handlers.ts b/webapp/nodejs/src/owner_handlers.ts
index 86c78e33..64bb5b71 100644
--- a/webapp/nodejs/src/owner_handlers.ts
+++ b/webapp/nodejs/src/owner_handlers.ts
@@ -4,14 +4,18 @@ import { secureRandomStr } from "./utils/random.js";
 import { setCookie } from "hono/cookie";
 import type { RowDataPacket } from "mysql2";
 import type { Chair, Ride } from "./types/models.js";
-import { calculateSale } from "./common.js";
+import { calculateSale, responseError } from "./common.js";
 import { ulid } from "ulid";
 
 export const ownerPostOwners = async (ctx: Context<Environment>) => {
   const reqJson = await ctx.req.json<{ name: string }>();
   const { name } = reqJson;
   if (!name) {
-    return ctx.text("some of required fields(name) are empty", 400);
+    return responseError(
+      ctx,
+      new Error("some of required fields(name) are empty"),
+      400,
+    );
   }
   const ownerId = ulid();
   const accessToken = secureRandomStr(32);
@@ -74,7 +78,7 @@ export const ownerGetSales = async (ctx: Context<Environment>) => {
     });
   } catch (e) {
     await ctx.var.dbConn.rollback();
-    return ctx.text(`${e}`, 500);
+    return responseError(ctx, e, 500);
   }
 };