PURPOSE: To obtain easily sinterable aluminum nitride powder giving a sintered compact excellent in characteristics such as heat conductivity by heat-treating aluminum nitride powder contg. less than a specified amt. of oxygen existing in the form of solid soln. in an oxygen-contg. atmosphere.

CONSTITUTION: Aluminum nitride powder contg. ≤0.6wt.% oxygen existing in the form of solid soln. is synthesized and heat-treated in an oxygen-contg. atmosphere to obtain the objective aluminum nitride powder contg. ≤0.6wt.% oxygen existing in the form of solid soln. and 0.4-2.0wt.% oxygen existing in the form of hydroxide, oxide or oxynitride. The synthesized aluminum nitride powder is usually heat-treated at 600-1,200°C in an atmosphere under 0.05-0.8 atm pressure of PO2 in a rotary kiln, a screw kiln, a batch kiln, etc.