An oil temperature sensor includes a housing assembly in which a lead frame on which a thermistor for detecting a temperature of oil is mounted is integrated with a housing such that a tip-side terminal portion is exposed outward. The housing includes a groove formed linearly into which a cable-attached terminal is inserted. The groove is opened on both sides of the groove in the extending direction and is also opened in one direction crossing the extending direction. A joint terminal portion and a sheath of a cable are partially inserted into the groove.