PURPOSE: To improve precision and lower the cost, by processing plastically the temperature sensing part and the transfer part different in diameter into one body with the same metallic material.

CONSTITUTION: Temperature sensing part 1 and a part of transfer part 2 different in diameter are produced into one body with the same metallic material by plastic processing other than welding connection. Since the tube for sensor is obtained by processing and finishing parts of a large outside diameter and a small outside diameter from one tube in this manner, fluid movement of the inside hole required most for intrumentation is smooth, so that precision can be improved, and omission of production processes can be performed.