The image forming apparatus prevents a transfer roller from slipping when discharge processing for supplying toner to a contact portion between a photosensitive drum and a cleaning blade is performed. The developing unit performs transfer operation to form band-like toner images on a photosensitive drum to supply a predetermined amount of toner to a contact portion between the photosensitive drum and a cleaning blade without causing the transfer roller to perform transfer operation, so that the predetermined amount of toner is supplied in a plurality of batches.