Disclosed is an apparatus of adjusting valve timing for internal combustion engine configured to adjust at least one valve timing of an intake valve and an exhaustive valve by torque of a cam shaft and pressure of working fluid, and a method thereof. The method of the present disclosure is such that a rotor is embedded with a hydraulic control valve configured to operate a locking pin member, and the hydraulic control valve is so configured as to have various control positions in order to supply or discharge working fluid in response to engine emergency stop or start and normal engine operational state whereby locking and releasing operations are realized with accurate responsiveness and reliability due to smaller working fluid through a passage and an engine performance can be improved by adjusting the valve timing.