An actuator (11) comprises a main plate (21), a frame (22), a connecting member (23), and a piezoelectric element (30). The main plate (21) has a main surface (201) and a main surface (202) and has a rotationally symmetrical shape in plan view. The frame (22) is disposed outside an outer peripheral edge (e21) of the main plate (21). The connecting member (23) connects the outer peripheral edge (e21) of the main plate (21) and the frame (22), and holds the main plate (21) such that the main plate (21) can vibrate in relation to the frame (22). A piezoelectric element (30) is disposed on the main surface (201) of the main plate (21), and the outer shape is smaller than the main plate (21). The main plate (21) is provided with a recess (210) and a thin portion (219) in an area that in plan view does not include a center (o21) and the outer peripheral edge (e21) of the main plate (21), and as a result, a low-elastic-modulus area is formed which has a lower elastic modulus than that of the portion of the center (o21).