PURPOSE: To obtain the compositionally gradient material varying in characteristics of both surfaces by mixing or laminating plate materials of powders consisting of plural materials in such a manner that the compsn. ratios thereof change gradually, sintering the laminated materials and applying plastic working to the laminated materials in their thickness direction.

CONSTITUTION: The powders or plate materials of metals and alloys, such as stainless steels, low-carbon steels, carbon steels and various alloys, which vary in the characteristics, such as heat resistance and mechanical strength, are mixed or superposed to form graded lamination layers a in such a manner that the compsn. ratios thereof change gradually in their thickness direction. After the graded lamination layers a are molded to a prescribed to form a preform b, the preform is subjected to sintering c at a high temp. and is further subjected to hot forging d by acting pressurizing force on the sintered body in its compsn. changing direction. After the thickness of the sintered body is reduced down to a thickness possible to roll, the sintered body is subjected to hot rolling e. The large-sized plate material, the two characteristics of which, i.e., the excellent heat resistance on one surface and the high mechanical strength on the other side face, change gradationally in the thickness direction is produced.