To provide a lead frame at a low cost capable of using a general-purpose heat plate in a resin sealing process wherein burrs of resin and defective shape attended with breaks, expansion, contraction, and exfoliation or the like of a resin film adhered to the rear side of the lead frame are hardly caused before resin sealing.

The lead frame 2 is configured to include a plurality of leads 4a, 4b formed with a prescribed arrangement so that an inverted-V shaped recessed part V or an inverted-U shaped recessed part U is formed to respective rear sides of wire bonding areas 5 of the leads 4a, 4b. In a wire bonding method disclosed herein, connection wires W are bonded at apexes or in the vicinity of them of the inverted-V shaped recessed part V or the inverted-U shaped recessed part U. A resin sealing semiconductor device 1 disclosed herein is configured to use the lead frame 2 that is sealed by embedding a resin even to the recessed part V or U.