diff --git a/server/internal/app/file.go b/server/internal/app/file.go
index 076d09d8a1..943f531f1a 100644
--- a/server/internal/app/file.go
+++ b/server/internal/app/file.go
@@ -1,12 +1,10 @@
 package app
 
 import (
-	"fmt"
 	"io"
 	"mime"
 	"net/http"
 	"path"
-	"time"
 
 	"github.com/labstack/echo/v4"
 	"github.com/reearth/reearth/server/internal/usecase/gateway"
@@ -26,7 +24,6 @@ func serveFiles(
 		return func(ctx echo.Context) error {
 			reader, filename, err := handler(ctx)
 			if err != nil {
-				fmt.Printf("file handler err: %s\n", err.Error())
 				return err
 			}
 			ct := "application/octet-stream"
@@ -53,25 +50,13 @@ func serveFiles(
 		"/export/:filename",
 		fileHandler(func(ctx echo.Context) (io.Reader, string, error) {
 			filename := ctx.Param("filename")
-
 			r, err := repo.ReadExportProjectZip(ctx.Request().Context(), filename)
 			if err != nil {
-				return nil, "", err
+				return nil, "", rerror.ErrNotFound
 			}
-			fmt.Printf("download: %s \n", filename)
-
-			go func() {
-				// download and then delete
-				time.Sleep(3 * time.Second)
-				err := repo.RemoveExportProjectZip(ctx.Request().Context(), filename)
-				if err != nil {
-					fmt.Printf("delete err: %s \n", err.Error())
-				} else {
-					fmt.Printf("file deleted: %s \n", filename)
-				}
-			}()
-
-			return r, filename, nil
+			// download and then delete
+			err = repo.RemoveExportProjectZip(ctx.Request().Context(), filename)
+			return r, filename, err
 		}),
 	)
 
diff --git a/server/internal/infrastructure/gcs/file.go b/server/internal/infrastructure/gcs/file.go
index a8a94d852c..9109421fd5 100644
--- a/server/internal/infrastructure/gcs/file.go
+++ b/server/internal/infrastructure/gcs/file.go
@@ -109,7 +109,7 @@ func (f *fileRepo) RemoveAsset(ctx context.Context, u *url.URL) error {
 func (f *fileRepo) ReadPluginFile(ctx context.Context, pid id.PluginID, filename string) (io.ReadCloser, error) {
 	sn := sanitize.Path(filename)
 	if sn == "" {
-		return nil, gateway.ErrInvalidFile
+		return nil, rerror.ErrNotFound
 	}
 	return f.read(ctx, path.Join(gcsPluginBasePath, pid.String(), sn))
 }
@@ -133,7 +133,7 @@ func (f *fileRepo) RemovePlugin(ctx context.Context, pid id.PluginID) error {
 
 func (f *fileRepo) ReadBuiltSceneFile(ctx context.Context, name string) (io.ReadCloser, error) {
 	if name == "" {
-		return nil, gateway.ErrInvalidFile
+		return nil, rerror.ErrNotFound
 	}
 	return f.read(ctx, path.Join(gcsMapBasePath, sanitize.Path(name)+".json"))
 }
@@ -170,7 +170,7 @@ func (f *fileRepo) RemoveBuiltScene(ctx context.Context, name string) error {
 
 func (f *fileRepo) ReadStoryFile(ctx context.Context, name string) (io.ReadCloser, error) {
 	if name == "" {
-		return nil, gateway.ErrInvalidFile
+		return nil, rerror.ErrNotFound
 	}
 	return f.read(ctx, path.Join(gcsStoryBasePath, sanitize.Path(name)+".json"))
 }
@@ -208,15 +208,20 @@ func (f *fileRepo) RemoveStory(ctx context.Context, name string) error {
 func (f *fileRepo) ReadExportProjectZip(ctx context.Context, name string) (io.ReadCloser, error) {
 	sn := sanitize.Path(name)
 	if sn == "" {
-		return nil, gateway.ErrInvalidFile
+		return nil, rerror.ErrNotFound
 	}
-	r, err := f.read(ctx, path.Join(gcsExportBasePath, sn))
+	bucket, err := f.bucket(ctx)
 	if err != nil {
-		if errors.Is(err, rerror.ErrNotFound) {
-			r, err = f.read(ctx, path.Join(gcsExportBasePath, name))
-		}
+		log.Errorfc(ctx, "gcs: read bucket err: %+v\n", err)
+		return nil, rerror.ErrInternalByWithContext(ctx, err)
 	}
-	return r, err
+	if ok := checkPrefix(ctx, bucket, gcsExportBasePath); !ok {
+		return nil, errors.New("Prefix not exist")
+	}
+	if ok := checkObject(ctx, bucket, gcsExportBasePath, path.Join(gcsExportBasePath, sn)); !ok {
+		return nil, errors.New("Object not exist")
+	}
+	return f.read(ctx, path.Join(gcsExportBasePath, sn))
 }
 
 func (f *fileRepo) UploadExportProjectZip(ctx context.Context, zipFile afero.File) error {
@@ -410,3 +415,38 @@ func newAssetID() string {
 	// TODO: replace
 	return id.NewAssetID().String()
 }
+
+func checkPrefix(ctx context.Context, bucket *storage.BucketHandle, prefix string) bool {
+	it := bucket.Objects(ctx, &storage.Query{
+		Delimiter: "/",
+	})
+	for {
+		attrs, err := it.Next()
+		if err == iterator.Done {
+			break
+		}
+		fmt.Printf("attrs.Prefix %s \n", attrs.Prefix)
+		if attrs.Prefix == prefix+"/" {
+			return true
+		}
+	}
+	return false
+}
+
+func checkObject(ctx context.Context, bucket *storage.BucketHandle, prefix string, objectName string) bool {
+	it := bucket.Objects(ctx, &storage.Query{
+		Prefix:    prefix + "/",
+		Delimiter: "/",
+	})
+	for {
+		attrs, err := it.Next()
+		if err == iterator.Done {
+			break
+		}
+		fmt.Printf("attrs.Name %s \n", attrs.Name)
+		if attrs.Name == objectName {
+			return true
+		}
+	}
+	return false
+}