An actuator has a shape memory alloy wire that contracts when heated by electric power supply and expands when cooled, whereby its length changes, a first hollow member through which the shape memory alloy wire is inserted, a movable element having an end mechanically connected to the shape memory alloy wire and movable relative to the first hollow member along a direction along which the length of the shape memory wire changes, an elastic member that is arranged between the movable element and the first hollow member and by which an external force is exerted on the movable element in a direction in which the shape memory alloy wire expands. In addition, an insulation member is joined to the movable element, a part of the insulation member is inserted in the first hollow member in a movable manner, and the shape memory alloy wire is connected to the end of the inserted part. Thus, the shape memory alloy wire is prevented from being in electrical contact with the elastic member.
