Thermal shock damage in ceramic disks heated from outside under constant heat flux conditions was evaluated from fragmentation of fractured specimens. Temperature disturibution in disk specimens in radial direction were measured to evaluate the thermal fracture stress and thermal fracture energy. Work-of-fracture of the specimen was estimated from the total area of the fractured surface, and the elastic strain energy was calculated from the nth-power functional fitting of measured temperature distributions at fracture. Two types of ceramics were used for the experiments; alumina ceramic having higher strength, elasticity and thermal couductivity, and mica ceramics having lower strength, elasticity and thermal conductivity. Work-of-fracture in thermal fractured specimens had a mutual relation with elastic strain energy, and corresponded to approximately one third of the total elastic strain energy. Furthermore, according to the thermal shock damage resistance of ceramics, the fracture energy varied with temperature distribition. Therefore, thermal shock test by heating disk specimens is effective to evaluate the thermal shock damage resistance of ceramics.