Method of measuring liquid level and liquid-level gauge

For measurement of a liquid level, an optical fiber connected at its one end portion to force receiving means movably arranged in liquid to receive force from the liquid is dipped in the liquid together with the force receiving means, and a change in the force acting on said force receiving means when the liquid level changes is detected as a change in strain in the optical fiber by means of an optical fiber strain gauge connected to the other end of the optical fiber, thus measuring a water level of the liquid.