An object of the present invention is to provide an electroless nickel-palladium-gold plating method which is able, when performed on a plating target surface such as terminals of a printed wiring board, terminals of other electronic components, and other resin substrates with a fine metal pattern, to prevent abnormal metal deposition on a resin surface which is an undercoat and to provide a high-quality plated surface. Another object of the present invention is to provide a plated product with a high-quality plated surface, particularly such as an interposer and motherboard, and a semiconductor apparatus using the same. These objects were achieved by the electroless nickel-palladium-gold plating method of the present invention, which is a method for plating target objects such as terminals of a printed wiring board and in which at least one surface treatment selected from a treatment with a solution of pH 10 to 14 and a plasma treatment is performed at an optional step after the step of providing a palladium catalyst and before the step of performing electroless palladium plating.