To enable documents to be either right- or left-bound so that double- leaved documents keep good appearance by controlling an image data processing means so that the directions and order of output of images on output paper are varied, so that a stapling process is effected as selected.

Paper printed is fed from a paper unloading part 10b to a finisher 1 comprising a paper folding means 2, a stapler means 3, etc. A selecting key for indicating the bound form of copying paper is located on the control panel of a copying machine 10, and either right- or left-binding is selected by operating the selecting key. To make documents double-leaved, either a mode in which two documents are copied on one paper or a mode in which one document is copied on one paper is determined. Then the binding direction is determined, and in the case of right-binding the even-numbered images in reading order are designated so that they are printed first. In the case of left-binding, the odd-numbered images are printed first, and the directions of the images are rotated 180°.