A ceramic body is heated to a predetermined temperature by using a furnace, and a cooling gas is ejected toward a first end face of the ceramic body so that the first end face of the ceramic body is cooled. At this time, the temperature of the first end face of the ceramic body is measured by a radiation thermometer provided on the same side from which the cooling gas is ejected, and the internal temperature is measured by a thermocouple provided in the ceramic body. Thereafter, a thermal shock resistance test in which actual use conditions are simulated is performed by obtaining the temperature gradient of the ceramic body from measurement results of the temperature of the first end face of the ceramic body and the internal temperature and checking the absence or presence of cracks that occurs to the ceramic body.
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