A battery temperature sensor includes a sensor body and an electric wire connecting connector. The sensor body includes a sensor housing configured to be detachably attached to a mating body, a first locking member provided on the sensor housing and configured to be locked to the mating body, and a temperature measuring element integrally formed in the sensor housing. The electric wire connecting connector includes a connector housing configured to be detachably attached to the sensor housing, a second locking member provided on the connector housing and configured to be locked to the sensor housing, and a pair of terminals attached to the connector housing. The terminals are electrically connected to the pair of leads respectively when the connector housing is coupled to the sensor housing.