PURPOSE: To form an electroless plating layer having good quality in the next process, by applying activating treatment due to a Pd-salt-containing treating liquid containing a specific complexing agent to a base disc such as an audio disc in an activating process as the preceeding process of electroless plating in fabricating said base disc.

CONSTITUTION: In fabricating a press mold of an audio disc or a video disc, a base disc is subjected to activating treatment as the preceeding process of electroless plating treatment used in fabricating said base disc. As an activating treatment liquid, a composition, which is prepared by adding 15g/l of NaCl, KCl, KBr or NH4Cl as a complexing agent to Pd to an aqueous solution containing 3g/l of palladium chloride, is used. Because this activating treatment liquid increases activating capacity, activating capacity becomes stable even if pH is set to an acidic region and an excellent electroless plating layer is obtained in the next electroless plating process.