PURPOSE: To enhance the filled rate of an insulating material, electrophotographic characteristics, such as photosensitivity, and mechanical strength by electrolytically treating a porous oxide film by a pulsative flow containing a negative component.

CONSTITUTION: The conductive substrate is subjected to a primary electrolytic treatment to form the porous oxide film, and this is subjected to a secondary electrolytic treatment by using the pulsative flow containing the negative component to form fine pores freed of ruggedness on the walls of the fine pores and enhanced in smoothness of the walls. When the secondary electrolytic treatment is executed for a long time by using the pulsative flow containing only the negative component, it is probable for the interface between the conductive substrate and the porous oxide film to be peeled off, and therefore, it is preferred to set a time length by considering the strength of the porous oxide film and the smoothness of the fine pores, thus permitting the obtained electrostatic recording body to be enhanced in the filled rate of the insulating material and improved in the electrophotographic characteristics, such as photosensitivity, and superior in mechanical strength.