Abstract: In a liquid supply nozzle having a nozzle valve opened and closed by the manipulation of an operating lever, a nozzle pipe having an air vent hole near the front discharge end thereof, and an automatic stopping mechanism operating when air supply thereto is shut off by the closure of the air vent hole to close the nozzle valve irrespective of the operation of the operating lever, there is provided a mechanism which normally keeps the air vent hole open but operates when the nozzle is pressed against the rim of a liquid filling inlet designed for supplying a liquid of a kind other than that of the liquid specified for the nozzle to close the air vent hole. As a result of the closure of the air vent hole by this vent hole closing mechanism, the nozzle valve is closed by the automatic fuel supply stopping mechanism even when the operating lever is operated, whereby supplying of the specified liquid into a liquid filling inlet designed for another kind of liquid is effectively prevented.