To avoid deficiency resulting from the careless disallowable state of a lock mechanism by setting the lock mechanism to an allowable state after conducting hydraulic control for holding the relative rotation angle of second rotation body in the case of the relative rotation of first and the second rotation bodies for valve timing control.

Valve timing is controlled in response to a relative rotation angle between a driven gear 22 (first rotation body) rotatably fitted to an intake side cam shaft 12 and an inner rotor 29 (second rotation body) contained in a housing 28. In this device, any of first hydraulic control delaying the relative rotation angle of the second rotation body, second hydraulic control advancing the relative rotation angle of the second rotation body, or third hydraulic control holding the relative rotation angle of the second rotation body is selectable. In the case of the first or the second hydraulic control in a predetermined relative rotation angle state, the third hydraulic control is precedently conducted, a lock mechanism is brought into an allowable state, and thereafter, the first or the second hydraulic control is conducted.