To provide a lead molding device for a semiconductor device, wherein defective bending of a lead which is mode with a bend roller punch, is reduced for improved manufacturing yield.

A pressing piece 23 and a bending die 38, which clamp and fix from the upper and lower a plurality of outer leads 15, arrayed in one direction, extend from a side surface 14 of an enclosure 13 of a semiconductor device 12, a bending roller punch 32 extending in the side surface 14 direction of the envelope 13 which bends the outer leads 15, while simultaneously rolling in the prescribed direction after hitting to the upper surface of a root part of the outer leads 15, and a back guide roller 36 provided in parallel so as to contact the outer side roller surface of the bending roller punch 32, are provided. Here, bending with the bending roller punch 32, and clamping and release of it with the semiconductor device 12 are performed in a series of actions.