PURPOSE: To prevent the damage of a conductive film and to surely impress a cathode voltage on the conductive film by energizing the conductive film of a film lined with the conductive film and a cathode through a conductive liq.
CONSTITUTION: A cathode contact tank 10 is provided at least on the preceding stage of a line, and a conductive liq. 12 is constantly supplied to a liq. feeding pipe 11 arranged in the tank 10. Cathodes 13 and 13 are vertically opposed to each other in the conductive liq. 12, a cathode voltage is impressed on the liq. 12, a film 1 lined with a conductive film passes through the liq. 12 between the cathodes 13 and 13, and a cathode voltage is impressed on the conductive film through the liq. 12.