In cylinder chambers 14 and 15 of a housing 10 constituting an actuator main body 13, racks 17 and 18, to both end portions of which piston portions 17a and 18a are provided, are reciprocably incorporated. A pinion 25 meshing with the racks 17 and 18 is provided on a rotary shaft 24 rotatably mounted to the housing 10. An inner ring 32 is incorporated inside an outer ring 41 fixed to the housing 10, and the inner ring 32 is attached to the rotary shaft 24 and rotates and drives a swung member. Rollers 43 serving as rolling elements are incorporated between an inner peripheral surface of the outer ring 41 and an outer peripheral surface of the inner ring 32, and the rotary shaft 24 and the inner ring 32 are rotatably supported by the outer ring 41 via the rollers 43.