PURPOSE: To form the optional porosity at low cost and high yield of a material without any pollution in a method for making the surface of a valve member used to oil impregnation porous.

CONSTITUTION: The valve member 1 is arranged in a mold 2 while forming a gap S between a sliding part of the valve member 1 and the mold 2. Mixed material of plural kinds of powders 3L, 3H having different m.p. is filled into the gap S. Thereafter, the mixed material is heated to the temp. of the m.p. or higher of-the low m.p. powder 3L, and the low m.p. powder 3L is melted, and based on this melting, by sticking the high m.p. powders 3H to each of the others, the porous part is formed at the sliding part.