PURPOSE: To obtain complex ceramics excellent in thermal shock resistance by blending boron nitride(BN) with aluminum nitride (AlN) and alumina at a specific ratio and sintering the blend.

CONSTITUTION: This complex ceramics comprises sintering mixed powder composed of 5-65wt.% of BN and the rest consisting of AlN and alumina and the weight ratio of AlN to alumina is (1:0.01) to (1:2.40). 0.05-20wt.% of one or more kinds of rare earth-based compounds containing alkaline earth-based compounds and Y can be added as ceramic components. The specific surface area of BN is preferably 1-250m2/g. These complex ceramucs are obtained by blending raw material powders, forming the resultant mixed powder and sintering the formed material. As the average particle diameters of raw material powders are preferably as follows: BN: 0.5μm; AlN: 0.5μm; alumina: 0.3μm; alkaline-earth-based and rare-earth-based compounds: ≤5μm. The mixing of powder is carried out by a ball mill, etc., using ethanol as a dispersing medium. Forming is carried out by hydrostatic pressing, etc., and the formed material is sintered in a non-oxidizing atmosphere.