diff --git a/src/main/java/tenten/blooming/domain/subgoal/controller/SubgoalController.java b/src/main/java/tenten/blooming/domain/subgoal/controller/SubgoalController.java
index 676f105..474f07b 100644
--- a/src/main/java/tenten/blooming/domain/subgoal/controller/SubgoalController.java
+++ b/src/main/java/tenten/blooming/domain/subgoal/controller/SubgoalController.java
@@ -1,6 +1,7 @@
 package tenten.blooming.domain.subgoal.controller;
 
 import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 import tenten.blooming.domain.subgoal.dto.CompletedGoalInfoResponse;
@@ -33,9 +34,13 @@ public ResponseEntity<ResponseUpdateSubgoal> updateSubgoal(
 
         responseUpdateSubgoal.setSubgoalName(findSubgoal.getSubgoalName());
 
-        List<LocalDate> doneDates = subgoalService.updateSubgoal(subgoalId);
-        responseUpdateSubgoal.setDoneDateList(doneDates);
-
+        try {
+            List<LocalDate> doneDates = subgoalService.updateSubgoal(subgoalId);
+            responseUpdateSubgoal.setDoneDateList(doneDates);
+        } catch (IllegalStateException e) {
+            responseUpdateSubgoal.setErrorMsg(e.getMessage());
+            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(responseUpdateSubgoal);
+        }
         return ResponseEntity.ok(responseUpdateSubgoal);
     }
 
diff --git a/src/main/java/tenten/blooming/domain/subgoal/dto/ResponseUpdateSubgoal.java b/src/main/java/tenten/blooming/domain/subgoal/dto/ResponseUpdateSubgoal.java
index d4becc4..bf4cf0d 100644
--- a/src/main/java/tenten/blooming/domain/subgoal/dto/ResponseUpdateSubgoal.java
+++ b/src/main/java/tenten/blooming/domain/subgoal/dto/ResponseUpdateSubgoal.java
@@ -13,4 +13,5 @@
 public class ResponseUpdateSubgoal {
     private List<LocalDate> doneDateList;
     private String subgoalName;
+    private String errorMsg = null;
 }
diff --git a/src/main/java/tenten/blooming/domain/subgoal/service/SubgoalService.java b/src/main/java/tenten/blooming/domain/subgoal/service/SubgoalService.java
index f0e8e6a..40ffa26 100644
--- a/src/main/java/tenten/blooming/domain/subgoal/service/SubgoalService.java
+++ b/src/main/java/tenten/blooming/domain/subgoal/service/SubgoalService.java
@@ -125,7 +125,6 @@ public List<LocalDate> addDoneDate(Long subgoalId) {
                 if(i > 0 && (Objects.equals(doneDates.get(i - 1), today))) {
                     throw new IllegalStateException("이미 체크된 TASK입니다.");
                 }
-                System.out.println(i);
                 switch (i + 1) {
                     case 1: {
                         findSubgoal.setDoneDate1(today);