To enable smooth removal of a socket without corotation with a stud bolt after completion of implanting the stud bolt.

Under a condition that the stud bolt 6 is implanted in a work 13, using a socket 1, a contact shaft 8 installed inside of a socket main body 2 presses a tip surface of the stud bolt 6 via balls 10, 10 installed between slopes 8a, 8a formed on an upper surface of the contact shaft 8 and a receiving surface 5a formed on a lower surface of a holder shaft member 5 connected to a fastening tool 3 to transmit fastening torque to the stud bolt 6. When the socket 1 is rotated in a reverse direction (a direction indicated by an arrow in the figure) for releasing fastening of the stud bolt 6, the balls 10, 10 roll in a direction ascending the slopes 8a, 8a. Consequently, the socket 1 is removed from the stud bolt 6 with no corotation of the stud bolt 6 and little resistance.