PURPOSE: To obtain the high-density sintered material which is free from compsn. deviation by subjecting the surface of sample powder to an electric discharge then to energization and heating up the sample powder by the Joule heat generated in such a manner at the time of sintering nitrides, oxides of unstable valency, etc., by a powder sintering method.

CONSTITUTION: A carbon mold 1 constituted to be fitted with upper and lower punches 2, 3 made of carbon is prepd. Stainless steel electrodes 4, 5 are brought into contact with the upper and lower punches 2, 3 and are electrically connected to a power source 6. The mold is so constituted that the entire part thereof can be pressurized from above and below by a hydraulic unit 7. The sample powder 10 is packed into the metallic mold 1 and pulse voltages are impressed between the two electrodes 4 and 5 to generate the discharge on the surface of the powder 10; thereafter, the powder is immediately energized and the mold 1 is heated by the Joule heat generated by this energization, by which the sintered compact is obtd. Oxides of iron and copper, nitrides of Ti, Zr, Hf, B, etc., are adequate as the sample powder 10.