To improve mounting workability by forming a guide groove gradually narrowing along the attaching direction toward an actuator fixing part on a contact surface between the actuator and its case, and forming an attaching part having an opening part communicating with the guide groove, on the rotary shaft of the actuator.

When an actuator 10 is attached to actuator fixing parts 6, 7, the actuator 10, is made to penetrate an actuator penetration part. Then, if the projecting part 5 of a rotary shaft end part 4 is positioned slantly, the length of the diagonal line of the projecting part 5 is larger than the width of the linear part 13a of a guide groove 13, then, the projecting part 5 hooks in the guide groove 13. If the projecting part 5 is lightly stuck, the projecting part 5 makes its turning motion and is stuck in the linear part 13a from a width expanding part 13b. In this way, the projecting part 5 can mesh with the attaching part 12 of the rotary shaft of the actuator 10. The actuator 10 is engagingly locked at its end part by means of the meshing claw 8 of the actuator fixing part 7. Thus, the actuator attaching work can be achieved easily.