diff --git a/src/main/java/com/kusitms/jipbap/auth/AuthExceptionHandler.java b/src/main/java/com/kusitms/jipbap/auth/AuthExceptionHandler.java
index 44e7287..d59c8ce 100644
--- a/src/main/java/com/kusitms/jipbap/auth/AuthExceptionHandler.java
+++ b/src/main/java/com/kusitms/jipbap/auth/AuthExceptionHandler.java
@@ -47,4 +47,11 @@ public CommonResponse<?> handleJsonException(JsonException e, HttpServletRequest
         log.warn("Auth-005> 요청 URI: " + request.getRequestURI() + ", 에러 메세지: " + e.getMessage());
         return new CommonResponse<>(ErrorCode.INTERNAL_SERVER_ERROR);
     }
+
+    @ExceptionHandler(UsernameExistsException.class)
+    @ResponseStatus(HttpStatus.BAD_REQUEST)
+    public CommonResponse<?> handleUsernameExistsException(UsernameExistsException e, HttpServletRequest request) {
+        log.warn("Auth-006> 요청 URI: " + request.getRequestURI() + ", 에러 메세지: " + e.getMessage());
+        return new CommonResponse<>(ErrorCode.EMAIL_EXISTS_ERROR);
+    }
 }
diff --git a/src/main/java/com/kusitms/jipbap/auth/AuthService.java b/src/main/java/com/kusitms/jipbap/auth/AuthService.java
index e8c8cdb..4ca716d 100644
--- a/src/main/java/com/kusitms/jipbap/auth/AuthService.java
+++ b/src/main/java/com/kusitms/jipbap/auth/AuthService.java
@@ -53,6 +53,7 @@ public class AuthService {
     public void signUp(SignUpRequestDto dto) {
 
         if(userRepository.existsByEmail(dto.getEmail())) throw new EmailExistsException("이미 가입한 이메일입니다.");
+        if(userRepository.existsByUsername(dto.getUsername())) throw new UsernameExistsException("이미 존재하는 닉네임입니다.");
         userRepository.save(
                 User.builder()
                         .id(null)
diff --git a/src/main/java/com/kusitms/jipbap/auth/exception/UsernameExistsException.java b/src/main/java/com/kusitms/jipbap/auth/exception/UsernameExistsException.java
new file mode 100644
index 0000000..3848ce2
--- /dev/null
+++ b/src/main/java/com/kusitms/jipbap/auth/exception/UsernameExistsException.java
@@ -0,0 +1,7 @@
+package com.kusitms.jipbap.auth.exception;
+
+public class UsernameExistsException extends RuntimeException{
+    public UsernameExistsException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/com/kusitms/jipbap/common/response/ErrorCode.java b/src/main/java/com/kusitms/jipbap/common/response/ErrorCode.java
index b18f161..a1909a8 100644
--- a/src/main/java/com/kusitms/jipbap/common/response/ErrorCode.java
+++ b/src/main/java/com/kusitms/jipbap/common/response/ErrorCode.java
@@ -19,6 +19,7 @@ public enum ErrorCode {
     INVALID_PASSWORD_ERROR(false, HttpStatus.BAD_REQUEST.value(), "비밀번호를 확인해주세요. 카카오 계정이라면 카카오 로그인으로 시도해주세요."),
     INVALID_ACCESS_TOKEN_ERROR(false, HttpStatus.BAD_REQUEST.value(), "AccessToken 정보를 찾을 수 없습니다."),
     INVALID_REFRESH_TOKEN_ERROR(false, HttpStatus.BAD_REQUEST.value(), "RefreshToken 정보를 찾을 수 없습니다."),
+    USERNAME_EXISTS_ERROR(false, HttpStatus.BAD_REQUEST.value(), "이미 존재하는 닉네임입니다."),
 
     //user
     USER_NOT_FOUND_ERROR(false, HttpStatus.BAD_REQUEST.value(), "존재하지 않는 유저입니다."),
diff --git a/src/main/java/com/kusitms/jipbap/user/User.java b/src/main/java/com/kusitms/jipbap/user/User.java
index 56a0452..fcc8b6f 100644
--- a/src/main/java/com/kusitms/jipbap/user/User.java
+++ b/src/main/java/com/kusitms/jipbap/user/User.java
@@ -30,6 +30,7 @@ public class User extends DateEntity {
     private String password; //비밀번호
 
     @NotBlank
+    @Column(unique = true)
     private String username; //닉네임
 
     @NotBlank
diff --git a/src/main/java/com/kusitms/jipbap/user/UserRepository.java b/src/main/java/com/kusitms/jipbap/user/UserRepository.java
index 8291b94..bcef93c 100644
--- a/src/main/java/com/kusitms/jipbap/user/UserRepository.java
+++ b/src/main/java/com/kusitms/jipbap/user/UserRepository.java
@@ -6,5 +6,6 @@
 
 public interface UserRepository extends JpaRepository<User, Long> {
     boolean existsByEmail(String email);
+    boolean existsByUsername(String username);
     Optional<User> findByEmail(String email);
 }