You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allimages gaicontinue="Timing_of_overpass_04_spring_actuator.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="668" ns="6" title="ファイル:Take off.png" imagerepository="local">
        <imageinfo>
          <ii timestamp="2014-09-01T00:45:27Z" user="Yasunari mimura" />
        </imageinfo>
      </page>
      <page pageid="818" ns="6" title="ファイル:Timing of overpass 01 bound ball.png" imagerepository="local">
        <imageinfo>
          <ii timestamp="2015-12-30T07:45:19Z" user="Yasunari mimura" />
        </imageinfo>
      </page>
      <page pageid="819" ns="6" title="ファイル:Timing of overpass 02 bound ball.png" imagerepository="local">
        <imageinfo>
          <ii timestamp="2015-12-30T07:45:45Z" user="Yasunari mimura" />
        </imageinfo>
      </page>
      <page pageid="820" ns="6" title="ファイル:Timing of overpass 03 bound ball spring.png" imagerepository="local">
        <imageinfo>
          <ii timestamp="2015-12-30T07:46:10Z" user="Yasunari mimura" />
        </imageinfo>
      </page>
    </pages>
  </query>
</api>