PURPOSE: To simply remove a fastening tool with a very small force by freely separating contact sections of a torque transmission mechanism from each other when a stud bolt is to be removed after it is fastened.

CONSTITUTION: When a drive shaft 5 is rotated in the opposite direction after a stud bolt is fastened, contact sections of a torque transmission mechanism 10 are separated from each other, thus a screw shaft section 6 is loosened by applying the rotary torque slightly smaller than the rotary force in the bolt fastening direction applied to a cylinder from a screw shaft section 6 to the drive shaft 5. When this screw shaft section 6 is rotated by the required angle, the torque transmission mechanisms 10 are brought into contact with each other, the cylinder 2 is rotated together with the screw shaft section 6, and a fastening tool is removed from the stud bolt.