In opening/closing control for the valve mechanism to which the return torque is applied in an opening direction or a closing direction of the valve, provided are a position control system for outputting a q-axis current command based on a position deviation between a target position command directed to the brushless DC motor and the coarse present position of the motor obtained by using the position detection sensor of a pulse output type, and a current control system in which a virtual current feedback is built for outputting a phase voltage command without a current sensor based on the q-axis current command and the coarse present position of the motor obtained by using the position detection sensor of the pulse output type.