PURPOSE: To partially silver-plate a lead frame having good external appearance by employing as a cathode current for partial silver-plating a single-phase rectified wave having specific ripple rate or higher.

CONSTITUTION: A rectified wave having many pulsation rate (ripple rate), i.e., a rectified wave having 120W157% of pulsation rate and particularly single-phase full-wave rectified wave is used for a partial silver-plating used for a lead frame to obtain a preferably plating external appearance and to further increase a placing current density. The frequency of the single-phase full-wave rectified wave to be used is 10Hz or higher and specially preferably approx. 10W200Hz, and the current density depends upon the composition of the plating solution or silver density, and preferably plating is generally obtained even by high current density of approx. 20W80A/dm2.