A method of the surface treatment of a porous material which comprises the step of electrolyzing the porous material in an electrolytic bath composed of an aqueous solution of at least one salt selected from the group consisting of alkali metal thiotungstate, alkali metal thioantimonate, alkali metal thiostannate, alkali metal thiocuprate, alkali metal thioarsenate, alkali metal thioaurate, alkali metal thioplatinate, alkali metal thioniobate, alkali metal thiovanadate, alkaline earth metal thiotungstate, alkaline earth metal thioantimonate, alkaline earth metal thiostannate, alkaline earth metal thiocuprate, alkaline earth metal thioarsenate, alkaline earth metal thioaurate, alkaline earth metal thioplatinate, alkaline earth metal thioniobate, alkaline earth metal thiovanadate, ammonium thiotungstate, ammonium thioantimonate, ammonium thiostannate, ammonium thiocuprate, ammonium thioarsenate, ammonium thioaurate, ammonium thioplatinate, ammonium thioniobate and ammonium thiovanadate, to thereby impregnate the porous material with the metallic sulfide. Optionally, the porous material may be immersed alternately in an aqueous solution prepared as described above for the electrolytic bath and an acid aqueous solution after the electrolysis to further impregnate the porous material with the metallic sulfide.