To provide a punching die for the lead frame, by which a metal plate on which a groove has been formed, can be punched with high precision without generating burrs.

In the punching die for the lead frame, by which the metal plate having a square groove 3 on its one side, is punched by a punch 4 in a pattern crossing this square groove 3, a projection 8 with a shape complementary to the sectional shape of the square groove 3, which enters the square groove 3 at the time of punching, is provided on the contact surface 5 of the tip of the punch 4. The height of the projection 8 is determined so that when the tip of the projection 8 has been lowered to a position where it comes into contact with the bottom of the square groove 3 or to a position just before the above position, a flat surface part 5b except the projection 8 of the contact surface 5 of the punch 4, comes into surface contact with the flat surface of the metal plate.