To heighten response performance for both of temperature rise and temperature decline of gas, in a temperature sensor in which a small diameter part having a relatively small outer diameter of tube is formed over a prescribed range in the longitudinal direction to the distal end on a portion a little to the distal end side of the tube, and a temperature sensor is arranged so as to be located on the distal end or the portion a little to the distal end side of the small diameter part.

A metal projection 81 projecting outward is provided only on a portion positioned on the furthermore rear than the rear end P1 of the element 21 on the outer circumferential surface of the small diameter part 13 of the tube 11. Since a heat receiving area is increased without increasing a tube thickness on the side of the element 21, measurement responsiveness during increase of a gas temperature is heightened. Further, since the projection 81 is provided on the furthermore rear than the element 21, a temperature of a portion of the tube 11 on the side of the element 21 is easily lowered following decline of the gas temperature, to thereby also heighten measurement responsiveness during lowering of the temperature.