An actuator includes a light reflection part having light reflectivity, a movable part having the light reflection part and being rotatable around a rotation center axis, a pair of connection parts connected to the movable part, and a support part that supports the pair of connection parts, and each of the connection parts includes a pair of beam members, a distance between the pair of beam members gradually increases from a first surface side toward a second surface side of the movable part when seen from a direction in parallel to the rotation center axis of the movable part, and given that a distance between ends at the first surface side of the pair of beam members is W1 and a thickness of the pair of beam members in a thickness direction of the movable part is t, the following expression (1) is satisfied. w 1