PURPOSE: To eliminate the unnecessary resin flash of a mounting hole by providing the top edge of an operating pin upper than the bottom edge of sealing resin when making a through hole by permitting the fixing pin of a top die to face the operating pin of a bottom die.

CONSTITUTION: When forming a mounting hole on sealing resin 1, a fixing pin 3a mounted on a top die 3 and an operating pin 4a mounted on a bottom die 4 are used, a belleville spring 4b is incorporated in the operating pin 4a and the structure permits the operating pin 4a to operate vertically. At that time, the top of the operating pin 4a is permitted to be upper than at least a resin-sealed bottom edge IC. Therefore, when the top die 3 and the bottom die 4 are clamped, the belleville spring 4b of the operating pin 4a accommodates the unevenness and the pins are adhered at the leading edge of the fixing pin 3a. Thus, the unnecessary resin flash of the mounting hole la is eliminated.