An ECU calculates a target working angle r, and determines a difference between the target working angle r and the previous value r′ of target working angle as a change rate v to be feedforward controlled. Further, the ECU determines a deviation to be corrected by feedback control from the target working angle r and an actual value that is input from a sensor as a hypothetical rate u. The change rate v and the hypothetical rate u are added together, and a control amount to be output, for example, a voltage E is determined by referring to a three-dimensional map M3 from the added set change rate (v+u) and the input target working angle r.