diff --git a/src/middlewares/auth.ts b/src/middlewares/auth.ts
index 535ed1ec..a0215b9d 100644
--- a/src/middlewares/auth.ts
+++ b/src/middlewares/auth.ts
@@ -1,18 +1,17 @@
 // 로그인된 상태에만 접근할 수 있는 라우터(rooms)를 위한 미들웨어입니다.
-import { type Request, type Response, type NextFunction } from "express";
+import type { RequestHandler } from "express";
 import { isLogin, getLoginInfo } from "@/modules/auths/login";
 
-const authMiddleware = (req: Request, res: Response, next: NextFunction) => {
-  if (!isLogin(req)) {
-    res.status(403).json({
+const authMiddleware: RequestHandler = (req, res, next) => {
+  if (!isLogin(req))
+    return res.status(403).json({
       error: "not logged in",
     });
-  } else {
-    const { id, oid } = getLoginInfo(req);
-    req.userId = id;
-    req.userOid = oid;
-    next();
-  }
+
+  const { id, oid } = getLoginInfo(req);
+  req.userId = id;
+  req.userOid = oid;
+  next();
 };
 
 export default authMiddleware;
diff --git a/src/middlewares/authAdmin.ts b/src/middlewares/authAdmin.ts
index af9c7b5d..cc79ef29 100644
--- a/src/middlewares/authAdmin.ts
+++ b/src/middlewares/authAdmin.ts
@@ -1,34 +1,32 @@
 // 관리자 유무를 확인하기 위한 미들웨어입니다.
-import { type Request, type Response, type NextFunction } from "express";
+import type { RequestHandler } from "express";
 import { isLogin, getLoginInfo } from "@/modules/auths/login";
 import { userModel, adminIPWhitelistModel } from "@/modules/stores/mongo";
 
-const authAdminMiddleware = async (
-  req: Request,
-  res: Response,
-  next: NextFunction
-) => {
+const authAdminMiddleware: RequestHandler = async (req, res, next) => {
+  const redirectUrl = req.origin ?? "/";
+
   try {
     // 로그인 여부를 확인
-    if (!isLogin(req)) return res.redirect(req.origin ?? "/");
+    if (!isLogin(req)) return res.redirect(redirectUrl);
 
     // 관리자 유무를 확인
     const { id } = getLoginInfo(req);
     const user = await userModel.findOne({ id });
-    if (!user?.isAdmin) return res.redirect(req.origin ?? "/");
+    if (!user?.isAdmin) return res.redirect(redirectUrl);
 
     // 접속한 IP가 화이트리스트에 있는지 확인
     const ipWhitelist = await adminIPWhitelistModel.find({});
-    if (!req.clientIP) return res.redirect(req.origin ?? "/");
+    if (!req.clientIP) return res.redirect(redirectUrl);
     if (
       ipWhitelist.length > 0 &&
-      ipWhitelist.map((x: any) => x.ip).indexOf(req.clientIP) < 0 // TODO: Remove any
+      ipWhitelist.map((x) => x.ip).indexOf(req.clientIP) < 0
     )
-      return res.redirect(req.origin ?? "/");
+      return res.redirect(redirectUrl);
 
-    return next();
+    next();
   } catch (e) {
-    return res.redirect(req.origin ?? "/");
+    return res.redirect(redirectUrl);
   }
 };
 
diff --git a/src/middlewares/errorHandler.ts b/src/middlewares/errorHandler.ts
index e0a7ba72..f130caa8 100644
--- a/src/middlewares/errorHandler.ts
+++ b/src/middlewares/errorHandler.ts
@@ -1,4 +1,4 @@
-import { type Request, type Response, type NextFunction } from "express";
+import type { ErrorRequestHandler } from "express";
 import logger from "@/modules/logger";
 
 /**
@@ -11,20 +11,17 @@ import logger from "@/modules/logger";
  * @param res - 응답 객체
  * @param next - 다음 미들웨어 함수. Express에서는 next 함수에 err 인자를 넘겨주면 기본 global error handler가 호출됩니다.
  */
-const errorHandler = (
-  err: Error,
-  req: Request,
-  res: Response,
-  next: NextFunction
-) => {
+const errorHandler: ErrorRequestHandler = (err, req, res, next) => {
+  logger.error(err);
+
   // 이미 클라이언트에 HTTP 응답 헤더를 전송한 경우, 응답 헤더를 다시 전송하지 않아야 합니다.
   // 클라이언트에게 스트리밍 형태로 응답을 전송하는 도중 오류가 발생하는 경우가 여기에 해당합니다.
   // 이럴 때 기본 global error handler를 호출하면 기본 global error handler가 클라이언트와의 연결을 종료시켜 줍니다.
-  logger.error(err);
   if (res.headersSent) {
-    return next(err);
+    next(err);
+  } else {
+    return res.status(500).send("internal server error");
   }
-  return res.status(500).send("internal server error");
 };
 
 export default errorHandler;
diff --git a/src/middlewares/information.ts b/src/middlewares/information.ts
index 0006ea40..91b3d66f 100644
--- a/src/middlewares/information.ts
+++ b/src/middlewares/information.ts
@@ -1,10 +1,6 @@
-import { type Request, type Response, type NextFunction } from "express";
+import type { RequestHandler } from "express";
 
-const informationMiddleware = (
-  req: Request,
-  res: Response,
-  next: NextFunction
-) => {
+const informationMiddleware: RequestHandler = (req, res, next) => {
   req.clientIP =
     (req.headers["x-forwarded-for"] as string | undefined) ||
     req.connection.remoteAddress;
diff --git a/src/middlewares/limitRate.ts b/src/middlewares/limitRate.ts
index d137892b..18a3203b 100644
--- a/src/middlewares/limitRate.ts
+++ b/src/middlewares/limitRate.ts
@@ -1,10 +1,10 @@
 import rateLimit from "express-rate-limit";
 
-const limiter = rateLimit({
+const limitRateMiddleware = rateLimit({
   windowMs: 15 * 60 * 1000, // 15 minutes
   max: 1500, // Limit each IP to 1500 requests per `window` (here, per 15 minutes)
   standardHeaders: true, // Return rate limit info in the `RateLimit-*` headers
   legacyHeaders: false, // Disable the `X-RateLimit-*` headers
 });
 
-export default limiter;
+export default limitRateMiddleware;
diff --git a/src/middlewares/originValidator.ts b/src/middlewares/originValidator.ts
index 3927d46e..330226cc 100644
--- a/src/middlewares/originValidator.ts
+++ b/src/middlewares/originValidator.ts
@@ -1,21 +1,17 @@
-import { type Request, type Response, type NextFunction } from "express";
+import type { RequestHandler } from "express";
 
-const originValidatorMiddleware = (
-  req: Request,
-  res: Response,
-  next: NextFunction
-) => {
+const originValidatorMiddleware: RequestHandler = (req, res, next) => {
   req.origin =
     req.headers.origin ||
     req.headers.referer ||
     req.session?.loginAfterState?.redirectOrigin; // sparcssso/callback 요청은 헤더에 origin이 없음
 
-  if (!req.origin) {
+  if (!req.origin)
     return res.status(400).json({
       error: "Bad Request : request must have origin in header",
     });
-  }
-  return next();
+
+  next();
 };
 
 export default originValidatorMiddleware;
diff --git a/src/middlewares/session.ts b/src/middlewares/session.ts
index 8cf0dcf8..3486154e 100644
--- a/src/middlewares/session.ts
+++ b/src/middlewares/session.ts
@@ -1,6 +1,6 @@
 import expressSession from "express-session";
 import { nodeEnv, session as sessionConfig } from "@/loadenv";
-import { type LoginInfo } from "@/modules/auths/login";
+import type { LoginInfo } from "@/modules/auths/login";
 import sessionStore from "@/modules/stores/sessionStore";
 
 // 세션에 저장할 데이터 타입을 지정합니다.
diff --git a/src/middlewares/validator.ts b/src/middlewares/validator.ts
index b4e1b0cf..aafb165a 100644
--- a/src/middlewares/validator.ts
+++ b/src/middlewares/validator.ts
@@ -1,18 +1,14 @@
-import { type Request, type Response, type NextFunction } from "express";
+import type { RequestHandler } from "express";
 import { validationResult } from "express-validator";
 
-const validatorMiddleware = (
-  req: Request,
-  res: Response,
-  next: NextFunction
-) => {
+const validatorMiddleware: RequestHandler = (req, res, next) => {
   const validationErrors = validationResult(req);
-  if (!validationErrors.isEmpty()) {
+  if (!validationErrors.isEmpty())
     return res.status(400).json({
       error: "validation : bad request",
     });
-  }
-  return next();
+
+  next();
 };
 
 export default validatorMiddleware;