Abstract: Disclosed is a ceramic composite consisting essentially of hexagonal boron nitride (h-BN), aluminum nitride and, if any, unavoidably formed aluminum oxynitride (AlON), and a sintering aid and/or a reaction product of the sintering aid with the above-mentioned components (h-BN, AlN and AlON), in which the total amount of the sintering aid and the reaction product is 0.01 to 5 parts by weight per 100 parts by weight of the sum of h-BN, AlN and AlON. This sintered body comprises AlN and AlON in a total amount of 45 to 5% by weight with 55 to 95% by weight of h-BN. Alternatively, this sintered body comprises AlN and AlON in a total amount of 80 to 5% by weight with 20 to 95% by weight of h-BN, the degree of anisotropy of the thermal conductivity of the sintered body (the ratio of the maximum thermal conductivity to the minimum thermal conductivity, the direction of the maximum thermal conductivity being perpendicular to the direction of the minimum thermal conductivity) being at least 2.