Abstract: An automatic document feeder for an image forming apparatus comprises first and second document trays each for stacking thereon one or more documents. A document feeding unit is provided for feeding the documents one by one from the first document tray in order from the uppermost one of the documents, while reversing the same upside down. A reversing convey unit is provided for receiving the document fed from the optical exposure portion and for feeding the same in a first direction toward the second document tray while reversing the same upside down, as well as a second direction opposite to the first direction. A first change-over member is provided for selectively connecting the optical exposure portion to the document feeding unit or the reversing convey unit.