Abstract: After copper of printed circuit board lined with copper foil is etched with an acidic etching solution containing chloride ions, the resulting etching solution containing copper ions is placed in a cathode compartment partitioned with a diaphram from an anode compartment, while placing a caustic soda solution in the anode compartment, and subjected to electrolysis. In the cathode compartment, copper is deposited on an electrode without any redissolution of the deposited copper, and recovered, whereas in the anode compartment chlorine formed on an anode is absorbed into the caustic soda solution without any discharge to the atmosphere. The etching solution thus freed from the copper ions is admixed with the same kind of chemicals as consumed by the etching, and used again as a regenerated etching solution.