A file includes a binding body which is superimposed with a plurality of binding sheets, a curved retaining portion which is curved in a direction in which the binding body extends when the cover is opened, a curved subsidiary portion arranged to fix a back portion thereof in a desired configuration. The binding body is provided adjacent to the curved retaining portion and has an arch-shape in a direction away from the inner side of a spine portion and the curved retaining portion is connected with a width less than a width of the spine portion to the inner side of the curved subsidiary portion at the outer side of the curved retaining portion to enable the end edge adjacently provided on the binding body to curve.