To provide an apparatus capable of manually caulking a rock washer with efficiency and accuracy.

A torque-controlling wrench 12 is provided on a rotating shaft 11 for tightening a polygonal head 3. The handle part 34 of the torque- controlling wrench 12 is rotated in such direction that loosens a bolt 2, so that the boss part 35 of a linking arm 32 rotating therewith rotates a first one-way clutch 26 mounted on the rotating shaft 11. Consequently a first cam 27 rotating integrally with the first one-way clutch 26 moves a first link 13 upwardly, thereby extracting the attachment 10 of the rotating shaft 11 from the polygonal head 3. A second cam 28 moves a second link 14 upwardly so as to rotate a caulking part 15 connected with its lower end, thereby bending the locking part 5 of a lock washer 4.