prepared by a reduction nitriding method was used the lattice constant of the aluminum nitride powder of comparative example a 1 and the oxygen and carbon contents thereof were checked and the values shown in table i were obtained in example b 1 first aluminum nitride powder according to example a 1 was pulverized by a ball made of aluminum oxide in wet condition using ipa isopropyl alcohol as a solvent dried and molded by uniaxial pressing at a pressure of 200 kgf cm 2 to obtain a disc form molded product of 50 mm in diameter u03c6 and about 10 mm in thickness subsequently the disc form molded product was housed in a graphite mold for sintering and maintained at a sintering temperature of 2000 u00b0 c for 4 hours while applying a pressure of 200 kgf cm 2 by a hot press and then cooled in this manner the aluminum nitride based ceramic sintered body of example b 1 was prepared in this example as the atmosphere during the sintering process a vacuum atmosphere was used in the range of room temperature to 1000 u00b0 c and a nitrogen gas atmosphere was used in the range of 1000 u00b0 c to the sintering temperature the lattice constant volume resistivity and carbon content of the aluminum nitride based ceramic sintered body of example b 1 were checked as a result the x ray diffraction pattern shown in fig3 and the values shown in table ii were obtained the lattice constant and carbon content were checked in the same methods as mentioned above the volume.