To accelerate heat conduction and improve response, by inserting material for accelerating heat conduction into the part between a sheath accommodating a thermocouple and a well for protecting the sheath from outside.

Material 20 for accelerating heat conduction is inserted into a gap between a sheath 4 and a well 5. Low melting point metal whose coefficient of volume expansion at the time of solid is approximate to that at the time of liquid is preferably used as the material 20. When an object 17 of temperature measurement in a structure body 10 for the object, like a fluid tube, is fused metal or the like, it is desirable that the material 20 is metal of the same kind as the object 17. By inserting the material 20 for accelerating heat conduction, the temperature of a junction point (junction point for temperature measurement) in the seath 4 is changed by the heat traveling from the side surface of the well 5 through the material 20 and the sheath 4. The response can be improved as the result that the heat conduction path is minimized.