PURPOSE: To increase the number of punches which are arrangeable radially along the circumferential direction of a work.

CONSTITUTION: Many swing punches 13 which are radially arranged along the circumferential direction of a work are supported oscillatably by the upper die 7 through a horizontal shaft 15. The end part of each swing punch 13 is connected to a paddling 9 through a slide driver 19. By the rising displacement of the paddling 9 when the paddling 9 is abutted on a drive block 2 as the upper die 7 is lowered, each swing punch 13 is oscillated, and piercing work is performed between the swing punch and a floating die 3.