In a case of switching the control mode between the reference timing control mode and the F/B control mode, when an engine speed is greater than or equal to a predetermined speed, and when target advanced amount of intake valve timing is lower than a switching threshold (vicinity of the most retarded timing), an intake VCT is switched into the reference timing control mode. And when engine speed is more than the predetermined rotating speed, and when the target retarded amount of exhaust valve timing is less than the switching threshold (vicinity of the most advanced timing), an exhaust VCT is switched to the reference timing control mode.