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>
    <allfileusages gafcontinue="Black_peppercorns_with_mortar_and_pestle.jpg|33" />
  </query-continue>
  <query>
    <pages>
      <page pageid="10" ns="2" title="使用者:黃志翔" />
      <page pageid="29" ns="2" title="使用者:李彥廷" />
      <page pageid="309" ns="0" title="鈹" />
      <page pageid="357" ns="0" title="二氧化矽" />
      <page pageid="940" ns="0" title="六年制學程/01/2014.06.04" />
      <page pageid="1099" ns="0" title="大隊接力" />
    </pages>
  </query>
</api>