PURPOSE: To prevent the breakage of punch and die and to prolong the life of die by setting the projections extending from the die top surface to the bottom surface so that the ridge line of the projection is made vertical from the upper end of the inner side surface of the die, at least, at three positions of the tapered inner side surface of the die.

CONSTITUTION: An inner side surface 1a of a die 1 is tapered so that the slug drops easily. The projection 4 is set, at least, at three points of this inner side surface 1a. The projection 4a is set in extending from the top surface of the die 1 at the inner side surface 1a of the die 1 to the bottom surface. The ridge line 4a is extended vertical from the upper end of the inner side surface 1a of the die 1 and set so as to be made the taper angle D with the inner side surface 1a And on the case for punching the lead frame, the lead frame is mounted on the die, when the punch punches the lead frame in the die, the punched scum 3 is lowered while keeping itself in almost horizontal state to the vertical direction along the ridge line 4a of the die, so the slug is prevented from blocking.