In a variable valve timing device, which varies the rotational phase of a camshaft through the relative rotation of a vane rotor and a housing and is provided with a lock mechanism that releases the lock thereof in response to the application of lock-release hydraulic pressure, the crank angle CCA at which the application of lock-release hydraulic pressure is commanded is set variably in accordance with the pressure of the oil supplied for the application so that the lock-release hydraulic pressure rises at a crank angle at which the state of the cam torque becomes suitable for lock-release without relying on changes of time needed for the lock-release hydraulic pressure to raise resulting from oil temperature.