PURPOSE: To sufficiently weld void and to increase the closeness on surface layer part of a sintered body by arranging raw material powder having less than the prescribed particle size to the surface layer part to be plastic-worked.

CONSTITUTION: By the plastic working of from roll rolling, etc., the sintered body surface layer part is made elaborately. At the time of forming the sintered body, the fine raw material powder having 200 mesh under particle size is arranged. Then, by the successive plastic work, the welding of the void is promoted and the elaborateness of the surface layer part is promoted.