To automatically punch an iron core forming member by alternatively cooperating a first auxiliary die attached to a first maine die and a second auxiliary die attached to a second main die and successively changing a phase in a rolling direction.

A steel plate 7 is supplied between a drawing type lower die 11 and a upper die 12. A holding block 24b is inserted between an upper face of a sub-punch 20 and a pressing body 26 by extending a cylinder 25b positioning on the upper face of a main punch 19 facing to a recessed part 14a of a main die 15. On the other hand, a cylinder 25a arranged close to a recessed part 14a of the rear face of the main die is retracted, further, at other three places of recessed parts 14b, 14c, 14d, all of the cylinders 25b of the main punch 19 side are retracted, all of the cylinders 25a of the main die 15 side are extended. Under this state, the pressing body is pressed, a key groove is formed at the recessed part 14a position, at other three places of the recessed parts 14b, 14c, 14d, a key groove is not formed but a round shape part of axial hole is formed.