diff --git a/src/main/java/org/ntlab/acanthus_server/resources/gallery/StrokesRest.java b/src/main/java/org/ntlab/acanthus_server/resources/gallery/StrokesRest.java
index 0276096..27dfea5 100644
--- a/src/main/java/org/ntlab/acanthus_server/resources/gallery/StrokesRest.java
+++ b/src/main/java/org/ntlab/acanthus_server/resources/gallery/StrokesRest.java
@@ -197,7 +197,7 @@
     @Path("/{aid}/pageMap/{pid}/layers/{layerNo}/strokes/{strokeNo}/positions")
     @GET
     @Produces(MediaType.APPLICATION_JSON)
-    public SortedSet<Position> getPositions(@PathParam("aid") Integer aid, @PathParam("pid") Integer pid,
+    public List<Position> getPositions(@PathParam("aid") Integer aid, @PathParam("pid") Integer pid,
                                             @PathParam("layerNo") Integer layerNo, @PathParam("strokeNo") Integer strokeNo) {
         var pages = gallery.getAnimationByAid(aid).getPages();
         var strokes = new ArrayList<Stroke>();
@@ -214,7 +214,11 @@
             }
         });*/
 
-        return strokes.get(strokeNo).getPositions();          // 呼び出したstrokesの情報を返す
+        List<Position> positions = new ArrayList();
+        for (Position p: strokes.get(strokeNo).getPositions()) {
+            positions.add(p);
+        }
+        return positions;          // 呼び出したstrokesの情報を返す
 //        if(animation != null) {
 //            return this.positions;
 //        }else{