To provide a simple method for measuring a liquid level of a liquid vessel capable of using a hose pump fluctuating in delivery, and capable of sufficiently working without additional parts.

A submergible pipe 2 for charging/discharging liquid to/from the vessel 1 is immersed into the liquid in the vessel, the pipe 2 is connected to a pump 5 via a piping system, a gaseous medium is introduced therein, the pressure P of the piping system starts from the environmental pressure P0 and rises up to the pressure P1 which varies by discharging the liquid column in the submergible pipe and generates discontinuity in the pressure. The pressure difference or the lapse of time t1 from the environmental pressure P0 to the P1 generating the discontinuous pressure fluctuation is measured. The liquid level of the vessel is calculated from the pressure difference or the laps of time t1.