PURPOSE: To produce a powder sintered body having high density and high quality with less energy consumption by preforming the powder of a metal or ceramics then compressing and sintering the preform in fluid at a specific temp.

CONSTITUTION: The metallic powder or the powder of the ceramics is packed into a vessel 2 made of a thin stainless steel sheet and is compressed to make a preform 3. The preform is put into the fluid 5 in a pressuring machine 4. A vitrified or other inorg. material such as glass or slag softened by heating or an org. material such as plastic, oil or silicon softened by heating is used for the fluid 5. The above-mentioned fluid 5 and preform 3 are heated to the temp. of ≥1/2 the absolute temp. or the m.p. of the powder raw material used and up to the m.p. by a heater 8 and are pressurized and compressed under 500kg/cm2 by a pressurizing piston 7, by which the preform is sintered. The sintered article is further forged to form the finer crystal and to improve the toughness of the sintered body if the raw material powder is the metal.