A PWM signal generation unit generates a PWM signal to drive a motor, based on a current value of the motor sampled by a current value sampling unit, a position or speed of the motor sampled by a motor sampling unit, and a position or speed of a driven object sampled by a driven object sampling unit. An operation stop unit stops the operation of any one of the motor sampling unit and the driven object sampling unit depending on the power stored in the DC link part and power to which the control power source can supply when the alternating-current power source fails.