An actuator includes an electric motor, a power transmission mechanism having a worm provided in a motor rotating shaft of the electric motor and a worm wheel engaging the worm, a drive member connected to the motor rotating shaft through the power transmission mechanism and displaced according to a rotation of the motor rotating shaft, a control device determining a rotational range of the motor rotating shaft between an initial position and a driven position, and an urging device provided in the motor rotating shaft and urging the motor rotating shaft to the initial position. In case electricity is supplied to the electric motor, the motor rotating shaft rotates to the driven position against an urging force of the urging device, and in case the electricity is not supplied to the electric motor, the motor rotating shaft is urged by the urging device to rotate to the initial position.