A sensor (101) is configured such that a seal member (71) is provided in a deformed manner through crimping of a portion of a tube (11) located toward a rear end (17c) of the tube (11). The seal member (71) is deformed such that a frontward-oriented surface (75), which is a bottom surface of a recess (74) formed in a front end (73) of the seal member (72), presses a rear end (45) of an insulation sheath (41) frontward. Consequently, a front end (21a) of a sensor element is pressed against a front end (12) of the tube (11) via the insulation sheath (41). By virtue of a pressing action induced by rubber-like elasticity, high sensor responsiveness is maintained over a long period of time.