To easily attach/detach a die, a jig, etc., to/from a bed, a ram, etc., by providing an electromagnet on a fitting part of the bed and the ram, and providing an electromagnet on a stock to be worked.

A circular recessed part 20 is pierced downward in a bed 2 and a ram 3 as a fitting part of a stock to be worked, and an electromagnet 4 is fitted in the recessed part 20. After a die 1 is loaded on the bed 2, the ram 3 is lowered so as to be abutted on the ram 3 and an upper die-set. A switch 5 is turned on in this state to energize the electromagnet 4, the magnetic force is generated in the electromagnet 4, the upper die-set 5 is fixed to the ram 3, and the lower die-set 5 is fixed to the bed 2. When the die 1 is detached, the switch 15 is turned off to disconnect energization in the electromagnet 4, the electromagnet 4 is demagnetized and the die-set 5 is detached from the bed 2 and the ram 3. When the die-set 5 has no magnetism, the electromagnet 4 is embedded in the die-set 5, and the die is fixed to the bed 2 and the ram 3 by the magnetic force of the electromagnet 4.