PURPOSE: To produce a sintered hard diamond tool material having excellent machinability by disposing diamond powder into a laminar state on the layer of a mixture composed of hard metallic compd. powder and binder metallic powder and treating the mixture under and at a high pressure and high temp.

CONSTITUTION: The mixture composed of 85W70wt% one kind among hard metallic carbide, nitride, boride, silicide, oxide, etc. and 15W30wt% metallic powder of Co, Ni or the alloy thereof, etc. as a binder in the stage of sintering is packed into a vessel made of a heat resistant material. The diamond powder is packed into the laminar state onto said mixture and is hermetically sealed thereon with a top cap made of a heat resistant mateial. Such vessel is put into a high-pressure and high-temp. generating apparatus and is treated for 10W120min at 1,400W1,700°C temp. and 53,500W62,000kg/cm2 pressure. The metal for binding melts to bind the hard metallic compd. and diamond. The vessel is then cooled and the pressure is returned to the atm. pressure, by which the sintered hard solid body dispersed uniformly with the diamond powder is formed and the diamond tool material is produced.