An actuator (1) is provided with: a movable part (120); a support part (110, 210) which supports the movable part; and a plurality of torsion bars (230) (i) each of which connects the movable part and the support part along a long direction such that the movable part is capable of swinging around a rotational axis which is along the long direction and (ii) which are arranged along a short direction; the farther each torsion bar is from the rotational axis, the smaller a spring constant of each torsion bar is.