To simply inspect whether or not a temperature sensor operates normally by respectively inserting a reference temperature sensor and the temperature sensor to be inspected to two holes formed at a load face of a conical base having a bottom face set at the side of a heater.

At least two holes are formed at a load face of a conical base 2 having a bottom face set at the side of a heater H. The holes are directed to the center of the bottom face. A temperature sensor 3 as a reference is inserted to one of the holes, and a temperature sensor 4 to be inspected is inserted to the other hole. The temperature sensor 4 is inspected on the basis of measured results of the temperature sensors 3, 4. When a heating temperature of the heater H to the conical base 2 is set from an input device 6, a temperature adjuster 5 takes the measured result of the temperature sensor 3 and turns on a relay contact 7 until a desired temperature is obtained, i.e., controls the temperature. The measured result taken from the temperature sensor 3 is displayed at a display device 8. A temperature relay 9 turns on a relay contact 10 when the set temperature agrees with the measured temperature of the temperature sensor 4, thereby lighting a display lamp.