PURPOSE: To absorb a large reaction force by abutting a stopper and movable side stopper main body to a stationary side stopper main body directly.

CONSTITUTION: In case of exceeding a specified operation range in the revolution of a rotating body, the elastic body 30a of the stationary side stopper 21 and a dog tip 26a are abutted, a dog 26 is slided in an arrow mark direction, the detecting part 25a of a limit switch 25 comes out of the projecting part 26c of the dog, overrun detection is performed and the power of a rotation driving part is cut off. With its drifting thereafter, it becomes a mechanical stopper with the working face 24a of a movable side stopper main body 24 and the elastic body 30a of the stationary side stopper main body 21 being abutted and the rotation is limited in the specified operation range. The reaction force of this time is absorbed by a movable shaft stopper main body and a fitting bolt 23, and the stationary side stopper main body 29 and a fitting bolt 15b.