NOVELTY - A suspension liquid containing electroconductive compound particles (3) is spray-coated and dried on the back surface of a base material (1) to form (A) electroconductive compound particles layer (2). Blast particles (4) with average particle diameter of 50-200 mu m are collided on the coated base material in the internal direction of the base material. The electroconductive compound particles which are not adhered to the base material and the surface impurities are wash-removed (C) to obtain electroconductive base material.    USE - Processing of base material (claimed) for separator of polymer electrolyte fuel cell.    ADVANTAGE - The base material having excellent electroconductive performance is manufactured. Since the blast particles having average particle diameter of 50-200 mu m is used, the distortion of the separator base material is reduced. Since the particles can be collided at low collision rate, the wear and tear of the blasting machine and repair or maintenance of the blasting machine are reduced.    DETAILED DESCRIPTION - A suspension liquid containing electroconductive compound particles with average particle diameter of 1-10 mu m and ethanol or water is spray-coated and dried on the back surface of a base material consisting of stainless steel plate, titanium or its alloy to form electroconductive compound particles layer. Blast particles with average particle diameter of 50-200 mu m are collided on the coated base material in the internal direction of the base material. The electroconductive compound particles which are not adhered to the base material and the surface impurities are wash-removed to obtain electroconductive base material.    DESCRIPTION OF DRAWING(S) - The drawing shows the explanatory view of the electroconductive processing method. (Drawing includes non-English language text)    Base material (1)    Electroconductive compound particles layer (2)    Electroconductive compound particles (3)    Blast particles (4)    Electroconductive compound particles layer formation process (A)    Electroconductive compound particles adhesion process (B)    Wash-removing process (C)