PRODUCTION OF OPTICAL DISK

PURPOSE: To send a defective glass thick plate again to a pretreating stage for electroless plating by deciding the glass thick plate as the defective glass thick plate when this glass thick plate is rested for the specified time after the end of the pretreating stage for electroless plating. CONSTITUTION: The glass thick plate 28 is transported by a transfer unit 61 into a plating layer 62 into which a nickel electroless soln. (NED soln.) controlled in pH and temp. is poured. Plating films are formed on the glass thick plate 28 by immersing the glass thick plate into the nickel electroless soln. (a process for immersion in the nickel electroless soln.). At this time, the glass thick plate 28 is vertically and repetitively oscillated within the nickel electroless soln. by the transfer unit 61, by which the adhesion of air bubbles generated by chemical reaction on the resist layer surfaces is prevented.