A lower movable electrode having line parts on the opposite end sides and a capacitor part on the central side, and an upper movable electrode having line parts on the opposite end sides and a capacitor part on the central side are arranged such that the capacitor parts face each other. Driving electrodes of actuators for driving the lower movable electrode and actuators for driving the upper movable electrode are provided so as to be isolated electrically from the lower movable electrode and the upper movable electrode. Electrostatic capacity is controlled by moving the lower movable electrode and/or the upper movable electrode through the actuators and/or thereby adjusting the distance between both capacitor parts.