To provide a cover area variable type file which makes it possible to easily make an entry by sliding a slide body when fill-in or writing is required while allowing documents or pieces of paper of different sizes to be filed with the minimum size.

The cover area variable type file is composed of the cover body which has a binder inside and corresponds to the paper of arbitrary size, a plate-like slide body which is provided so as to correspond to the front or back cover of the cover body, and a slide mechanism that makes the slide body slide on the front cover of the cover body.