The image forming apparatus includes a printer that performs image printing on the sheet members supplied at preset intervals at the first transport speed and a processor that performs development processing on the printed sheet members transported at the second transport speed. The printer includes a distribution unit and a control section. The distribution unit distributes the sheet members into plural lines while transporting the sheet members at the first transport speed. The distribution unit is replaceable and has a distribution processing capacity corresponding with the sheet output amount per unit time required by the image forming apparatus. The control section controls one or both of the sheet supply intervals and the sheet distribution speed in accordance with the sheet output amount.