An actuator mounting section includes a plate member including a first plate and a second plate. The first plate is formed with an opening which accommodates an actuator element. The second plate includes a main body portion which overlaps the first plate and supporting portions which support opposite ends of the actuator element. A narrow portion narrower than the first plate is formed at a part of the main body portion of the second plate. A weld seal portion is formed by laser-welding the first plate and the second plate at the narrow portion. Adhesive is provided between the opposite ends of the actuator element and an inner surface of the opening of the first plate.