PURPOSE: To enable a composition to be simplified and facilitated, by using a synthetic resin member for a base member, and by forming the member to serve also as a rotation limiting member.

CONSTITUTION: On a base member 20, a rotor loose-fitting section 22 and a stopper section 24 are formed, and also, the rotor loose-fitting section 22 and a concentric ring-formed groove 26, and a through hole 28 bored through the center of the rotor loose-fitting section 22 and with a rotary shaft 30 penetrated through are integrally formed. The whole unit is almost elliptically formed, and near the outer periphery in the direction of the long diameter, bolt slots 29A, 29B to penetrate bolts through for fitting a three-positional rotary shaft actuator after assembly, on a driven member are bored through. Because such a complicated shape is required, the base member 20 is molded with resin to form said respective components integrally. Accordingly, the composition can be, of course, simplified and facilitated, and the impact noise of stopper sections 10, 24 is attenuated, and a magnetic influence upon a driven unit can be extremely suppressed.