An image reading apparatus includes: a command unit which generates a command signal periodically; a reading unit which reads an original in accordance with the command signal every time the command signal is generated; a conveying unit which conveys at least one of the reading unit and the original so as to change a relative position between the reading unit and the original; a signal output unit which outputs a displacement signal every time the relative position is changed by a predetermined amount corresponding to a reading interval; and a control unit which controls a generation timing of the command signal by the command unit. A generation period of the command signal is less than an output time interval of the displacement signal.