To provide a post-processing apparatus for enabling a bunch of sheets and a single sheet to be folded in simplified structure, and further enabling the folded sheet and sheets that are not folded to be mixed and bound, the post-processing apparatus has a processing tray to collate and collect sheets to perform binding processing, and a folding processing path having a folding processing section, and a folded sheet carrying-out path for carrying out a folded sheet is provided on the downstream side of the folding processing path. Then, the folded sheet carrying-out path is comprised of a circulating path for guiding the folded sheet again to the folding processing section, a post-processing path for guiding the folded sheet to the processing tray to perform post-processing, and a sheet discharge path for guiding the folded sheet to a storage stacker.