To reduce an influence due to the heat emission of an orifice to a cylinder hole by forming the orifice at a spot separating from the cylinder hole.

An orifice 51 is formed on one axial flat end face of the disc part 10 of a rotor 2, and extends from this end face in a direction perpendicular to a check valve attaching hole 20 to compose a valve body accommodating chamber 27 and opens to the inner periphery of the check valve attaching hole 20. Therefore a working oil to flow out from the cylinder hole 14 flows into the orifice 51 through the valve body accommodating chamber 27. Namely, the chamber 27 is used as a part of both a leading-in path and a leading-out path. When the orifice 51 is opened to the check valve attaching hole 20, since the orifice 51 separates farther from the cylinder hole 14 in comparison with a case where the orifice 51 is directly opened to the cylinder hole 14, a harmful influence to the cylinder hole 14 caused by heat generated when a working oil passes through the orifice 51 can be reduced.