PURPOSE: To improve the variable responsive property, controllable property of valve timing and the durability of a device.

CONSTITUTION: A timing pulley 10 is provided on the tip of a cam shaft 1 and a ring gear 25 is interposed between both 1, 10 and the ring gear 25 are provided on both axial sides with respective hydraulic chambers 26, 27 between the cam shaft 1 and timing pulley 10. Oil pressure is selectively supplied to respective hydraulic chambers 26, 27 by an oil control valve(OCV) 44 to move axially the ring gear 25 and relatively pivot the cam shaft 1 and timing pulley 10. A modulation valve 81 is provided between an oil pump 41 and the OCV 44. Thus, when pump discharged pressure from the oil pump 41 exceeds a fixed value, pressure introduced into the OCV 44 reaches almost a predetermined value, and oil pressure supplied to the OCV 44 does not exceed the predetermined value even if the temperature, viscosity, etc., of lubricating oil are changed and the rotational frequency of an engine is increased.