To solve the problems of difficulty of always holding at a prescribed angle the mirror surface of a mechanical type optical switch having many sliding places and causing friction to the extent that cannot be disregarded, and of large power consumption.

An actuator device includes a rotary shaft supported freely rotatably, a rotor magnet which is fixed to the rotary shaft and composed of the a permanent magnet with two magnetized poles, a means for regulating a first rotational position when the rotary shaft rotates in one direction, a means for regulating a second rotational position when the rotary shaft rotates in the other direction, and a means for driving the rotary shaft and the rotor magnet. A self hold state is formed by a yoke arranged so that one magnetic pole of the rotor magnet and the other pole form a closed magnetic circuit at least at either rotational position of the first rotational position and the second rotational position.