An intake valve phase setting unit sets the target valve phase used in the variable valve timing control based on the engine operating state, and a control target value setting unit sets the control target value based on the target valve phase. An actuator operation amount setting unit prepares the rotational speed command value for an electric motor that serves as an actuator of a variable valve timing system based on the deviation of the current value from the control target value. A phase change rate control unit sets the rate of change in the valve phase to a lower value when the variable valve timing control moves the valve phase away from the reference phase (the phase when the engine is idling) at which combustion takes place stably in engine than when the variable valve timing control causes the valve phase to the reference phase.