PURPOSE: To enable molten material to protrude hardly to the vicinity of the blowout part of a lead by a method wherein a part of the lead to be cut is formed thinner than its other part before a tie bar which links the leads together is cut and the leads and a frame are blown out.

CONSTITUTION: A blowout part 25 of a lead is formed thinner than the other part as compressed into the shape of the tip of a lead pre-processing punch 19 provided to a lead pre-processing die 18. Therefore, at cutting by fusion, even if the molten material protrudes to the periphery of the blowout part 25, it hardly becomes thicker than the lead, in result the molten material protrudes little in the thicknesswise direction of the lead at the blowout part 25. By this setup, in a forming process by a forming die, a lead is less deformed, because a molten material protrudes little.