Abstract: The present invention aims to stabilize the plating film and to even the thickness thereof in the case where through holes of printed wiring boards are subjected to copper plating.Copper recovered from the etching waste liquor produced in the general manufacture of the printed wiring boards is supplied from a powder feeder 21 into a dissolution tank 23 to obtain a copper ion solution. For the copper plating, a substrate 1 acting as a cathod is arranged facing anodes 28 within a plating tank 26. The dissolution tank 23 supplies the copper ion solution into a plating tank 26 to maintain at a predetermined value the concentration of copper ions of a plating solution 27. This allows the insoluble polar plate to be used as the anodes 28, which leads to a stable current density.