In an image forming apparatus capable of turning over a sheet to form images on both sides of the sheet, when duplex printing is executed successively on three or more sheets, a controller causes a first sheet conveyed from an image forming unit and a second sheet conveyed from the image forming unit to be guided into a first path by positioning a guide member in a first position, and then conveyed into a third path by a first roller, and causes a third and subsequent sheets conveyed from the image forming unit to be guided into a second path by positioning the guide member in a second position, and then conveyed into the third path by a second roller.