An automatic document feeder includes: a recording-medium set unit, on which a recording medium is set; a recording-medium set detecting unit that detects whether the recording medium is set on the recording-medium set unit; a conveying unit that conveys the recording medium; a sheet-feeding cover section that constitutes part of the conveying unit and that includes an openable and closable sheet feeding cover; and a control unit that separately receives a power-on signal, which is output when a power source of an image forming device including the automatic document feeder is turned on, and an energy-saving return signal, which is output when a return is made from an energy saving state where a power source of part of the device is disconnected. When the power-on signal is received, the control unit performs an initialization operation to initialize each unit of the automatic document feeder.