diff --git a/core/api_coupon.go b/core/api_coupon.go
index 74fd4dd..1dc0c7c 100644
--- a/core/api_coupon.go
+++ b/core/api_coupon.go
@@ -202,7 +202,12 @@ func downloadCoupons(mongoClient gocommon.MongoClient, w http.ResponseWriter, r
 	roundnum := binary.BigEndian.Uint32(roundObj[:])
 	var coupons []string
 	for _, uid := range coupon.Remains {
-		coupons = append(coupons, makeCouponKey(roundnum, []byte(uid)))
+		decUid, err := hex.DecodeString(uid)
+		if err != nil {
+			logger.Println("downloadCoupons Fail", err)
+			continue
+		}
+		coupons = append(coupons, makeCouponKey(roundnum, decUid))
 	}
 
 	enc := json.NewEncoder(w)
@@ -279,6 +284,23 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 		round, _ = coupon.MakeCouponRoundHash(code)
 	}
 
+	// 쿠폰 사용 유무 검사
+	alreadyused, err := mongoClient.Exists(CollectionCouponUse, bson.M{
+		"_id":    acc,
+		"rounds": round,
+	})
+	if err != nil {
+		logger.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if alreadyused {
+		// 이미 이 라운드의 쿠폰을 사용한 적이 있다.
+		w.WriteHeader(http.StatusConflict)
+		return
+	}
+
 	var coupon couponDoc
 	roundObj, _ := primitive.ObjectIDFromHex(round + round + round)
 	if len(key) == 0 {
@@ -299,7 +321,8 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 	} else {
 		// 쿠폰을 하나 꺼냄
 		matched, _, err := mongoClient.Update(CollectionCoupon, bson.M{
-			"_id": roundObj,
+			"_id":     roundObj,
+			"remains": key,
 		}, bson.M{
 			"$pull": bson.M{"remains": key},
 		})
@@ -333,41 +356,6 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 		return
 	}
 
-	alreadyused := false
-
-	// 무한 쿠폰인지 일회용 쿠폰인지 구분
-	// 쿠폰 사용 유무 검사
-	if coupon.Total == -1 {
-		already, err := mongoClient.Exists(CollectionCouponUse, bson.M{
-			"_id":    acc,
-			"rounds": round,
-		})
-		if err != nil {
-			logger.Println(err)
-			w.WriteHeader(http.StatusInternalServerError)
-			return
-		}
-
-		alreadyused = already
-	} else {
-		already, err := mongoClient.Exists(CollectionCouponUse, bson.M{
-			"rounds": round,
-		})
-		if err != nil {
-			logger.Println(err)
-			w.WriteHeader(http.StatusInternalServerError)
-			return
-		}
-
-		alreadyused = already
-	}
-
-	if alreadyused {
-		// 이미 이 라운드의 쿠폰을 사용한 적이 있다.
-		w.WriteHeader(http.StatusConflict)
-		return
-	}
-
 	if len(coupon.Effect) == 0 {
 		// 쿠폰이 없네?
 		w.WriteHeader(http.StatusBadRequest)