A seeded substrate is first prepared. The seeded substrate includes an insulation substrate having a main surface composed of a first region and a second region other than the first region, and a conductive seed layer provided on the first region. Subsequently, a conductive layer is formed on at least the second region to obtain a first treated substrate. An insulation layer is then formed on the first treated substrate. The seed layer is then exposed. A metal layer is then formed on the surface of the seed layer. Here, a voltage is applied between the anode and the seed layer while a solid electrolyte membrane containing a metal ion-containing solution being disposed between the second treated substrate and the anode, and the solid electrolyte membrane and the seed layer being pressed into contact with each other. Thereafter, the insulation layer and the conductive layer are removed.