To eliminate pointed parts from a die for forming a cavity.

An escape part 28, continued to the inner wall of a through hole 23 with a shape of recessing in stepped shape, is formed in a region corresponding to a coming-out stopper projection 27 out of a taper face 24 of a cavity 21. When forming a region which corresponds to the coming-out stopper projection 27 out of the cavity 21, a first die 30A for forming the through hole 23 and the front part of the pull-off stopper projection 27 and a second die 30B for forming the side face of the coming-out stopper projection 27 and the side face of the escape part 28 are contacted by sliding, and the first die 30A is stamped out frontward and the second die 30B is stamped out backward. When forming the non-corresponding region which does not correspond to the coming-out stopper projection 27 out of the cavity 21, a third die 30C which forms the through hole 23 and the region other than the escape part 28 out of the taper face 24 is used.