PURPOSE: To control a valve timing stably regardless of operating condition of an internal combustion engine and secular deterioration of parts.

CONSTITUTION: A control unit 14 is constituted as a microcomputer system, and provided with a fuzzy CPU 146. In the control unit 14, fuzzy inference is carried out on the basis of an internal combustion engine rotational speed detected by a rotational speed sensor 111, a cooling water temperature detected by a temperature sensor 121, a cam angle detected by an angle sensor 131, and current which flows in the coil of a control valve 153 detected by a shut resistance 154, and a current set value (Id) is decided. A spool stored in the control valve 153 is displaced in proportion to the set value (Id), and the angle of a cam displaced by a speed proportional to the set value (Id) is changed in an actuator 163.