In a substrate like a printed circuit board comprising an insulator and a copper layer laminated on part of the insulator, the insulator outer surface and the copper layer outer surface are simultaneously subjected to (1) a process including treatment with an alkali metal hydroxide solution, (2) a process including treatment with an alkaline aqueous solution containing an aliphatic amine, (3) a process including treatment with an alkaline aqueous solution having a permanganate concentration of 0.3 to 3.5 wt % and a pH of 8 to 11, (4) a process including treatment with an acidic microemulsion aqueous solution containing a thiophene compound and an alkali metal salt of polystyrenesulphonic acid, and (5) a process including copper electroplating, which are implemented sequentially.