An image forming apparatus comprising: a conveyor (100F3) configured to convey a recording medium; an image forming device (102, 100F1) configured to form an image on the recording medium conveyed from the conveyor (100F3); a reversing device (100F2) configured to reverse the recording medium in the image forming apparatus after the image forming device (102, 100F1) forms the image; and an output tray disposed above the image forming device (102, 100F1), wherein the reversing device (100F2) comprises a path configured to temporarily store the recording medium, and the path comprises an opening which allows the recording medium to be temporarily conveyed onto the output tray; wherein the conveyor (100F3) conveys the recording medium to eject the recording medium to the output tray with the image on the recording medium facing down or conveys the recording medium to a post-processing apparatus with the image on the recording medium facing up, and wherein the image forming device (102, 100F 1) performs image formation from a first page of recording media when the image forming device (102, 100F1) performs the image formation on one side of the recording media and the conveyor conveys the recording media to eject the recording media to the output tray, and wherein, when the image forming device (102, 100F1) performs the image formation on one side of the recording media and the conveyor (100F3) conveys the recording media to the post-processing apparatus: the image forming device (102, 100F1) performs image formation from a last page of recording media; or the image forming device (102, 100F1) performs image formation from a first page of recording media, and the reversing device (100F2) reverses the recording media. a conveyor (100F3) configured to convey a recording medium; an image forming device (102, 100F1) configured to form an image on the recording medium conveyed from the conveyor (100F3); a reversing device (100F2) configured to reverse the recording medium in the image forming apparatus after the image forming device (102, 100F1) forms the image; and an output tray disposed above the image forming device (102, 100F1), wherein the reversing device (100F2) comprises a path configured to temporarily store the recording medium, and the path comprises an opening which allows the recording medium to be temporarily conveyed onto the output tray; wherein the conveyor (100F3) conveys the recording medium to eject the recording medium to the output tray with the image on the recording medium facing down or conveys the recording medium to a post-processing apparatus with the image on the recording medium facing up, and wherein the image forming device (102, 100F 1) performs image formation from a first page of recording media when the image forming device (102, 100F1) performs the image formation on one side of the recording media and the conveyor conveys the recording media to eject the recording media to the output tray, and wherein, when the image forming device (102, 100F1) performs the image formation on one side of the recording media and the conveyor (100F3) conveys the recording media to the post-processing apparatus: the image forming device (102, 100F1) performs image formation from a last page of recording media; or the image forming device (102, 100F1) performs image formation from a first page of recording media, and the reversing device (100F2) reverses the recording media. the image forming device (102, 100F1) performs image formation from a last page of recording media; or the image forming device (102, 100F1) performs image formation from a first page of recording media, and the reversing device (100F2) reverses the recording media.