diff --git a/backend/internal/service/sms_service.go b/backend/internal/service/sms_service.go
index 26aab0a1..1c57c664 100644
--- a/backend/internal/service/sms_service.go
+++ b/backend/internal/service/sms_service.go
@@ -43,6 +43,9 @@ func (s *SmsServiceImpl) SendSms(to, content string) error {
 	apiURL := fmt.Sprintf("https://sens.apigw.ntruss.com/sms/v2/services/%s/messages", s.serviceID)
 	log.Printf("Requesting SENS API URL: %s", apiURL)
 
+	// Naver SENS API requires phone number without '+'
+	sanitizedTo := strings.Replace(to, "+", "", 1)
+
 	reqBody := domain.NaverSmsRequest{
 		Type:        "SMS",
 		ContentType: "COMM",
@@ -51,7 +54,7 @@ func (s *SmsServiceImpl) SendSms(to, content string) error {
 		Content:     content,
 		Messages: []domain.SmsMessage{
 			{
-				To: to,
+				To: sanitizedTo,
 			},
 		},
 	}