A carbon atmosphere thermometer 10a has: a thermocouple having thermocouple wires 16, 18, a thermocouple temperature measuring junction 14, and an insulating tube 12; a first protection tube 20 surrounding the thermocouple, while at least partially spaced apart from the thermocouple wires 16, 18 and others of the thermocouple; and a second protection tube 22 surrounding the first protection tube 20, while at least partially spaced apart from the first protection tube 20. For this reason, it becomes feasible to protect the thermocouple from the external environment, while preventing the thermocouple from reacting with the first protection tube 20. Furthermore, it becomes feasible to protect the thermocouple and the first protection tube 20 from the external environment, while preventing the first protection tube 20 from reacting with the second protection tube 22.