Abstract: There is provided a lead frame for an optical semiconductor device, an optical semiconductor device using such lead frame, and a manufacturing method for these, where the optical semiconductor device exhibits favorable brightness over a long period of time by preventing discoloration and degeneration of a plating layer provide on the lead frame and a resulting reduction in a reflection coefficient for light emitted from a light emitting element, even when using silicone resin as a sealing resin. An Ag—Au alloy plating layer 22 is formed on the surface of a pure Ag plating layer 21 on a lead frame 10 sealed chloroplatinic acid-containing silicon resin, so as to prevent direct contact between the layer 21 and the silicone resin. This suppresses the formation of AgCl due to a reaction with a hardening catalyst of the silicon resin, thereby preventing the Ag plating layer from turning a blackish-brown color.