An expansion and contraction actuator has a first long actuator portion and a second long actuator portion that face each other and connection members that connect the long sides of each of the first long actuator portion and the second long actuator portion to each other, in which a part of the first long actuator portion and a part of the second long actuator portion are apart from each other to thereby form a hollow structure, the first long actuator portion and the second long actuator portion each have a pair of long electrodes and a long electrolyte layer having an electrolyte, long internal electrodes thereof are the same cathode or anode electrodes, long external electrodes thereof are counter electrodes thereto, and the actuator expands and contracts in the direction of the screw axis by voltage application.