An image forming apparatus or an image forming system, includes a control section to control, at the time of forming an image by using a long sheet with a conveying direction sheet length longer than that of a sheet with a fixed paper size, so as to perform image formation by arranging multiple images on the long sheet, and the control section controls so as to form images repeatedly with a predetermined cycle on the long sheet, detects a margin region being a region where images are not formed on the long sheet, and controls image formation so as to dispose a patch image on the margin region.