diff --git a/src/main/java/org/swmaestro/repl/gifthub/auth/entity/User.java b/src/main/java/org/swmaestro/repl/gifthub/auth/entity/User.java
index 19f6b325..9eaa75a5 100644
--- a/src/main/java/org/swmaestro/repl/gifthub/auth/entity/User.java
+++ b/src/main/java/org/swmaestro/repl/gifthub/auth/entity/User.java
@@ -31,7 +31,7 @@ public class User extends BaseTimeEntity implements UserDetails {
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
 	private Long id;
 
-	@Column(length = 60, nullable = false, unique = true)
+	@Column(length = 60, nullable = false)
 	private String username;
 
 	@Column(length = 60)
diff --git a/src/main/java/org/swmaestro/repl/gifthub/auth/repository/UserRepository.java b/src/main/java/org/swmaestro/repl/gifthub/auth/repository/UserRepository.java
index 5f62009a..f02937fb 100644
--- a/src/main/java/org/swmaestro/repl/gifthub/auth/repository/UserRepository.java
+++ b/src/main/java/org/swmaestro/repl/gifthub/auth/repository/UserRepository.java
@@ -8,4 +8,6 @@ public interface UserRepository extends JpaRepository<User, Long> {
 	User findByUsername(String username);
 
 	User findByNickname(String nickname);
+
+	User findByUsernameAndDeletedAtIsNull(String username);
 }
diff --git a/src/main/java/org/swmaestro/repl/gifthub/auth/service/AuthService.java b/src/main/java/org/swmaestro/repl/gifthub/auth/service/AuthService.java
index c93721ed..c3d085ad 100644
--- a/src/main/java/org/swmaestro/repl/gifthub/auth/service/AuthService.java
+++ b/src/main/java/org/swmaestro/repl/gifthub/auth/service/AuthService.java
@@ -40,7 +40,7 @@ public class AuthService {
 	public JwtTokenDto signUp(SignUpDto signUpDto) {
 		User user = User.builder()
 				.username(signUpDto.getUsername())
-				.password(passwordEncoder.encode(signUpDto.getPassword()))
+				.password(signUpDto.getPassword())
 				.nickname(signUpDto.getNickname())
 				.role(Role.USER)
 				.build();
@@ -132,7 +132,7 @@ private JwtTokenDto generateJwtTokenDto(User user) {
 	 */
 	@Transactional
 	public void signOut(String username, SignOutDto signOutDto) {
-		User user = userRepository.findByUsername(username);
+		User user = userRepository.findByUsernameAndDeletedAtIsNull(username);
 		if (user == null || user.getDeletedAt() != null) {
 			throw new BusinessException("존재하지 않는 사용자입니다.", StatusEnum.UNAUTHORIZED);
 		}
diff --git a/src/main/java/org/swmaestro/repl/gifthub/auth/service/UserService.java b/src/main/java/org/swmaestro/repl/gifthub/auth/service/UserService.java
index a28cb38f..896eb2e3 100644
--- a/src/main/java/org/swmaestro/repl/gifthub/auth/service/UserService.java
+++ b/src/main/java/org/swmaestro/repl/gifthub/auth/service/UserService.java
@@ -62,7 +62,7 @@ public User create(User user) {
 	}
 
 	public boolean isDuplicateUsername(String username) {
-		return userRepository.findByUsername(username) != null;
+		return userRepository.findByUsernameAndDeletedAtIsNull(username) != null;
 	}
 
 	public boolean isValidatePassword(String password) {
@@ -74,7 +74,7 @@ public boolean isValidatePassword(String password) {
 	}
 
 	public User read(String username) {
-		User user = userRepository.findByUsername(username);
+		User user = userRepository.findByUsernameAndDeletedAtIsNull(username);
 		if (user == null) {
 			throw new BusinessException("존재하지 않는 회원입니다.", StatusEnum.NOT_FOUND);
 		}
@@ -104,7 +104,7 @@ public List<User> list() {
 	}
 
 	public UserUpdateResponseDto update(String username, Long userId, UserUpdateRequestDto userUpdateRequestDto) {
-		User user = userRepository.findByUsername(username);
+		User user = userRepository.findByUsernameAndDeletedAtIsNull(username);
 		if (user == null) {
 			throw new BusinessException("존재하지 않는 회원입니다.", StatusEnum.NOT_FOUND);
 		}
@@ -166,7 +166,11 @@ public OAuth deleteOAuthInfo(User user, OAuthPlatform oAuthPlatform) {
 
 	@Override
 	public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
-		return userRepository.findByUsername(username).getDeletedAt() == null ? userRepository.findByUsername(username) : null;
+		User user = userRepository.findByUsernameAndDeletedAtIsNull(username);
+		if (user == null) {
+			throw new UsernameNotFoundException("존재하지 않는 회원입니다.");
+		}
+		return user;
 	}
 
 	public List<OAuth> deleteOAuthInfo(User user) {