When the reception section has received a duplex printing instruction, the operation control section controls an sheet feeding unit to feed one sheet, and controls an image forming unit to form an image of a first page on one side of the sheet, and controls the sheet conveying unit to discharge the sheet. When the reception section has received an instruction indicating that the discharged sheet is an unused sheet with the formed image, the operation control section controls the sheet feeding unit to feed one sheet set in a manual feed tray, and controls the image forming unit to form an image of a second page on the other side of the sheet. The operation control section controls the feeding unit to feed a sheet, and controls the image forming unit to form images of a third page and subsequent pages on both sides of the sheet.