Abstract: There is provided a semiconductor device and a lead frame in which the cross section of bent portions (5a, 5b) of a gull wing type external lead (3) having a plurality of bent portions (5a, 5b) is arranged so that the width of bended inside is formed wider than that of the outside. By forming the external lead (3) in this manner, the external lead (3) of the lead frame is stably formed, and when the semiconductor device is mounted on a printed circuit board (9), a solder fillet is sufficiently formed about the bent portion (5b), and the connecting reliability can be made increased.