A motor current is estimated based on a target motor speed, an actual motor speed, and an engine speed. When the estimated motor current exceeds a predetermined value equivalent to a heat limiting current value, a variation (motor speed F/B amount) of the target motor speed outputted to an EDU from an ECU is restricted so that the motor current was restricted and heat generation in motor is restricted. In consideration of a deterioration of responsivity of the variable valve timing control due to restriction of the motor current during execution of motor current restriction processing, an existence of the abnormalities of variable valve timing controller is determined based on a deviation of the target camshaft phase and the actual camshaft phase.