The document feeder apparatus is equipped with a sheet supply unit including a sheet supply member for supplying an original to a reading position; a transport unit including a transport member for receiving the original from the sheet supply member and transporting the original to the reading position; a discharge unit including a discharge member for discharging the original read at the reading position; and a flat plate shape support frame for supporting the respective units. The sheet supply unit and discharge unit are mounted on one of front and rear sides of the support frame, and the transport unit is mounted on the other of the front and rear sides of the support frame, so that each unit is unitized. Further, a sheet supply opening for guiding the original from the sheet supply unit to the transport unit is established on one side of the support frame, and an opening for guiding the original from the transport unit to the discharge unit is established on the other side of the support frame.