An actuator includes a motor, an input rotation member driven by the motor, an input contacting portion formed on the input rotation member, a bush disposed so as to be relatively rotatable to the input rotation member, a first contacting portion and an engaging portion formed on the bush, a spiral spring including an outer circumferential hook portion in contact with the input contacting portion of the input rotation member, and an inner circumferential hook portion engageable with the engaging portion of the bush, the spiral spring storing a rotational force of the input rotation member as an potential energy via the input contacting portion, an output member disposed so as to be relatively rotatable to the input rotation member, an output contacting portion formed on the output member and in contact with the outer circumferential hook portion of the spiral spring; the output contacting portion transmitting the potential energy stored in the spiral spring to the output member; wherein the bush includes a second contacting portion positioned at a predetermined angle with the first contacting portion in a rotational direction of the bush and, the second contacting portion formed so as to contact with the input rotation member and the output member during the rotation of the bush relative to the input rotation member and the output member.