A motor control unit performs driving control for a stepping motor by using vector control, and detects a rotational position θ of a rotor of the stepping motor, the rotational position θ being required for vector control, by using a position detection unit, based on a pulse signal that is output from an encoder. The motor control unit determines whether or not there is an abnormality in the pulse signal output from the encoder. Upon determining that there is an abnormality in the pulse signal, the motor control unit corrects a detection value of the position θ of the rotor of the stepping motor so as to compensate an error caused by the abnormality in the pulse signal.