PURPOSE: To simplify working and improve work efficiency by using four cam drivers to drive many cams and providing a cam guide groove in only one cam driver.

CONSTITUTION: When a punch holder 25 is lowered, a member 17 fixes a shell 1 to a member 10 and sets it to a die 3. Then, the fourth cam driver 44 abuts on a stopper 71 and projections 32, 35 of a punch come into contact with worked parts 30, 33. Further, only the first and second cam drivers 41, 42 come down while the third and fourth cam drivers are at a stand-still. Pressing force is applied from the first cam driver 41 to the upper face of the first cam part 37 that fits to a groove 49, and the second cam part 38 moves on the faces 59, 60. The cam 36 and punch 31 shift in the direction F, and the projection of a punch 32 forms a concavity on the worked part 30. A punch 34 lowers together with the first cam driver 41 and a concavity is formed on the worked part 33 by the projection of the punch 35.