The purpose of the present invention is to provide a post-processing apparatus capable of performing conveying to and storing at a predetermined stack tray without causing sheet jamming even when a sheet having larger size than a standard size is introduced. The present invention comprises a post-processing apparatus as a processing tray on which sheets conveyed in a predetermined conveyance direction are stacked into a bundle shape, an aligning device which aligns the sheets conveyed to the processing tray, a binding device which performs a binding process on the sheets aligned by the aligning device, and a controller which controls the aligning device so that a sheet is aligned at a position being apart from the binding device by a predetermined distance when the sheet conveyed to the processing tray has a predetermined size or larger.