An image forming apparatus has an image reading portion sequentially generating image data of pages, a printing portion sequentially printing, a discharge portion sequentially discharging printed sheets, and a control portion making the discharge portion discharge the printed sheets to a set discharge position. The control portion detects the page numbers of a precedent read page and of a subsequent read page and sets, when the page numbers are not consecutive, the discharge position of the printed sheet corresponding to the subsequent read page to a different position from the discharge position of the printed sheet corresponding to the precedent read page.