getting error while trying to batch upload photos on fan page via Facebook javascript SDK

[admin]

I am trying to batch upload photos via Facebook javascript API. I did reading the API docuemnt.
(<a href="https://developers.facebook.com/docs/graph-api/reference/v2.0/page/photos" rel="nofollow">https://developers.facebook.com/docs/graph-api/reference/v2.0/page/photos</a>
<a href="https://developers.facebook.com/docs/graph-api/making-multiple-requests" rel="nofollow">https://developers.facebook.com/docs/graph-api/making-multiple-requests</a>)

I make batch request via the following javascript function:

function batchUploadPhotoOnPage() {
    var pageId = '111222333';
    var pageAccessToken = 'xxxxyyyzzzzzzz';
    FB.api(
        '/',
        'post',
        {
            'batch': [
                  {
                      'method': 'post',
                      'relative_url': pageId+'/photos',
                      'access_token': pageAccessToken,
                      'message': 'Test Upload Photos 1...'+new Date(),
                      'url': 'https://hn85599112.files.wordpress.com/2014/07/girl-photo.jpeg'
                  },
                  {
                      'method': 'post',
                      'relative_url': pageId+'/photos',
                      'access_token': pageAccessToken,
                      'message': 'Test Upload Photos 2...'+new Date(),
                      'url': 'http://www.paopaoche.net/up/2012-5/20125523231510353173.jpg'
                  }
             ]
        },
      function(response) {
          log(response);
      }
    );
}

But it always response an error message:

{
   "error": { 
      "message": "(#324) Requires upload file", 
      "type": "OAuthException", 
      "code": 324
   }
}

I am struggling for this a long time, but still can't figure it out. Please help, if you know where I am wrong. Many thanks! T_T