A sensor includes contact springs placed in contact with electrode terminals on major surfaces of a sensor device. At least one of the contact springs includes a spring contact portion, a spring holding portion, a spring bent portion, and a spring connecting portion. The spring contact portion contacts an outer surface of one of the electrode terminals. The spring holding portion is turned from the spring contact portion and extends outside the spring contact portion so as to overlap the spring contact portion in the contacting direction. The spring bent portion is bent inwardly from the spring holding portion and extends at a given angle to the contacting direction. The spring connecting portion is bent from the spring bent portion and extends in the axial direction of the sensor. Such a structure enables the contact spring to be reduced in size and thickness without sacrificing a required mechanical strength thereof.