An image forming apparatus 1, which has sophisticated functions of feeding recording paper of various sizes selectively and sorting printed paper, is available in a reduced size. With the feed bin sorters 31a-31d, the output bin sorters 32a-32j, and the output tray 33 being arranged in tiers, pre-printed paper is supplied from any of the feed bin sorters, whereas printed paper is delivered to any of the output bin sorters or the output tray.