LIQUID LEVEL DETECTION DEVICE OF LIQUID SUPPLYING APPARATUS, LIQUID LEVEL DETECTION METHOD FOR LIQUID SUPPLYING APPARATUS, AND LIQUID SUPPLYING APPARATUS EQUIPPED WITH SUCH LIQUID LEVEL DETECTION DEVICE

A liquid supplying facility includes: a tank in which a liquid is stored and a high-pressure gas is enclosed; a discharge pipe for discharging the liquid in the tank to outside with the high-pressure gas; and a valve, disposed in the discharge pipe, for switching a communication state between the tank and the outside. A liquid level detection device for the liquid supplying facility includes: a lower pipe which is in communication with a liquid-phase section of an interior space of the tank, the liquid-phase section being occupied by the liquid; an upper pipe which is in communication with a gas-phase section of the interior space of the tank, the gas-phase section being disposed above the liquid-phase section and occupied by the high-pressure gas; a differential pressure gauge for detecting a differential pressure between the lower pipe and the upper pipe; and a liquid level calculation part for calculating a liquid level of the tank on the basis of a differential pressure detection result of the differential pressure gauge. An inside of the upper pipe is filled with a filling liquid at least in a partial range.