PURPOSE: To simply control impregnation liquid while effectively utilizing the impregnation liquid by making a sintered nickel substrate to be impregnated with an active material not exceeding specific % of a fixed impregnation amount for the sintered nickel substrate by an electrolytic impregnation method while the residual active material is used for impregnation by a chemical impregnation method.

CONSTITUTION: When impregnating a substrate with an active material by electrolytic impregnation, the ratio of electrolytic impregnation is stopped at the impregnation amount not exceeding 55% and thereafter, the impregnation liquid becoming unable to be used for said electrolytic impregnation liquid is used for chemical impregnation thus making the residual nitrate of nickel component in the impregnation liquid is almost used for impregnation of the substrate. Thereby, the impregnation liquid having increased ammonium ions can be reused for chemical impregnation without requiring any treatment thus simply enabling to effectively utilize the impregnation liquid. Further, the impregnation liquid used for electrolytic impregnation is completely used for chemical impregnation of the same substrate thus simplifying control of the impregnation liquid.