To provide a method by which the generation and growth of whiskers in a plated coating including a tin-plated layer comprising tin (Sn) or a tin alloy can be suppressed to the utmost.

The method comprises: forming a Sn-plated layer 2 comprising Sn or a Sn-alloy; then forming an intermediate layer 3 made of a metal having a melting point higher than Sn on the surface of the Sn-plated layer 2; and forming a Sn-plated layer 4 arranged in the outermost surface of the plated coating, comprising Sn or a Sn-alloy and having a film thickness thinner than that of the Sn-plated layer 2 on the intermediate layer 3. Because the Sn-plated layer 4 arranged in the outermost surface of the plated coating is plated into a thin film, the generation of whiskers is suppressed, and the growth of whiskers is also suppressed because the intermediate layer 3 inhibits the supply of Sn atoms to the Sn-plated layer 4 from the Sn-plated layer 2.