To improve discharge efficiency from a discharge port and improve operation performance of valve timing by providing a connecting passage connecting the discharge port of a selector valve and the suction side of an oil pump.

A vane is rotated by an actuator to change the angle of a cam of a camshaft, for example when valve timing is set a target advance value, the spool valve 30 of a selector valve 18 is held on a neutral point on which all an inflow port 22, an advance port 24, and a lag port 26 are made in the shut-off state. When the advance port 24 or the lag port 26 of the selector valve 18 is connected to a discharge port 28, the discharge port 28 is connected to the suction side of an oil pump 12 through a connecting passage provided with a valve 52. Hereby discharge efficiency is raised by pump suction force, and accompanying this angular velocity of the vane is raised, to improve the operation performance of valve timing is improved.