Silicon carbide ceramics with equiaxed grain structure were obtained by hot-pressing at 2000°C in a vacuum with the aid of sufficient amounts of Al2O3 and Y2O3 as sintering additives. The thermal conductivity of the SiC ceramics was investigated using a laser-flash technique and a pure polycrystalline 6H-SiC prepared by Lely's method for bulk crystal growth for comparison purposes. Experimental results revealed that the thermal conductivity of the SiC ceramics, consisting primarily of 6H, 4H and 3C polytypes with various concentrations, appeared to exhibit a strong dependence upon the content as well as the polytype of the SiC at lower temperatures, the dependence, however, became less pronounced at elevated temperatures. Solid-solution and inhomogeneity are assumed to play an important role in further reducing phonon mean free path of the ceramics. A considerable deviation in thermal resistivity between the SiC ceramics and the pure 6H-SiC was observed. A difference in the temperature dependence of phonon mean free path compared with the theoretical expectation was discussed.