An electroless Ni-P plating method according to the present invention includes the steps of: providing a substrate including an insulating substrate and a copper alloy layer that has a predetermined pattern including a plurality of island portions that are isolated from each other; providing a plating solution to carry out electroless Ni-P plating; providing a solid piece including Ni, Ni-P, Co or Co-Ni on at least the surface thereof; and bringing the solid piece into contact with the surface of at least two of the island portions that are both in contact with the plating solution, thereby selectively forming an electroless Ni-P plated coating on the surface of the island portions. Thus, the present invention provides a Ni-P plating method that can subject the copper pattern on the insulating substrate to high-precision selective Ni-P plating on an industrial basis.