A lead frame for semiconductor device is provided with an inner lead part and an outer lead part. A composite plating layer is provided on the entire plane of a base material constituting the lead frame or at least on the outer lead part. The composite plating layer includes a base layer composed of an Ni-based plating layer formed on the entire plane of the base material constituting the lead frame or at least on the outer lead part, a Pd or Pd alloy plating layer formed on an upper plane of the base layer with a thickness of 0.005-0.01 .mu.m, and an Au plating layer formed on an upper plane of the Pd or Pd alloy plating layer with a thickness of 0.02-0.1 .mu.m. The lead frame for semiconductor device has a Pd-PPF structure. In the case of mounting a semiconductor device on a board and the like with a lead-free Sn--Zn based solder or other lead-free solders by using the lead frame, wettability of the lead frame with the lead-free Sn--Zn based solder or other lead-free solders is improved and mountability of the semiconductor device can be improved.