To equally apply an adhesive agent without wasting it by providing a form enough for sealing a melton dumbbell into the cavity of a lower die for an upper die, and an adhesive agent passage for introducing the adhesive agent into a gap between the melton dumbbell of the lower die and the peripheral edge of the cavity.

A melton dumbbell 3 is fitted to a cavity 4 of a lower die 2 preferably while turning the face in contact with the surface of a ball downward, and the melton dumbbell 3 is compressed and fixed by an upper die 1. The lower die is provided with an airhole 14, one of the upper die 1 or the lower die 2 is provided with an 0 ring 13 for preventing the adhesive agent from being leaked and inside the upper die 1, the injection passage for the adhesive agent is provided on a top plate from an injection port 5 to an injection groove. Then, the seam adhesive agent quantitatively injected from the seam adhesive agent injection port 5 through a syringe or an injection instrument is injected from the adhesive agent injection groove to the gap between the lower die 2 and the melton dumbbell 3 and applied. In this case, the quantity to be applied is determined by the length of a guide fin 11.