Thermal shock resistance of 80Al2O3-20Al composite and monolithic alumina ceramics was compared. Fracture strength was measured by using a 4-pont bending test after quenching. Thermal stresses of the ceramics and ceramic-metal composites were calculated using a finite element analysis. The bending strength of the Al2O3 ceramics decreased catastropically after quenching from 20$0^{circ}C$ to $0^{circ}C$. The bending strength of the composite also decreased after quenching from 200~2$25^{circ}C$, but the strength reduction was much smaller than for Al2O3. The maximum thermal stress occured in the monolithic alumina ceramics when exposed to a temperature difference of 20$0^{circ}C$ was 0.758 GPa. The same amount of stress occured in the Al2O3-Al composite when the temperature difference of 205$^{circ}C$ used.