The present invention accurately detects a steering turn-back caused by steering torque fluctuations and minimizes the effects of the steering turn-back on the stability of a control system, and suppresses steering torque fluctuations during a turn-back to reduce discomfort experienced by a driver. The present invention comprises: a turn-back detection unit that determines that a steering turn-back has begun if a motor rotational speed is at or below a set speed, a motor rotational acceleration is in a direction in which the motor rotational speed becomes zero, and the motor rotational acceleration is at or above a set acceleration; and a current command control unit that outputs, on the basis of the steering torque or the motor rotational speed, a current command to the motor. If the turn-back detection unit has determined that a steering turn-back has begun, the current command control unit increases a transmission gain from the input to the output of the current command control unit.