A document feeder includes a feed tray, a catch tray, a carrying path extending from the feed tray to the catch tray via a scanning position, a reversal path diverging from a point on the carrying path downstream relative to the scanning position and connecting to a point on the carrying path upstream relative to the scanning position, a switchback mechanism conveying a sheet back to front from the reversal path toward the scanning point, an ejection mode switching mechanism having a flap provided upstream relative to the catch tray movably relative to an ejection roller, the ejection mode switching mechanism switching an ejection mode by moving the flap between a first mode to eject the sheets on already-ejected sheets and a second mode to insert the sheets under already-ejected sheets. The flap forms part of the reversal path in the first mode.