PURPOSE: To make possible the exact and easy measurement of the level of a soln. of which the specific dielectric constant is unknown or fluctuates by installing a reference electrode so as to be fully submerged into the soln. to be measured.

CONSTITUTION: An electrode 1 for measuring the soln. level and reference electrode 2 which face each other and consist respectively of two poles are set into the soln. 3 of which the liquid level is going to be measured. The electrode 1 is immersed in the soln. 3 for the length L from the bottom end and the electrode 2 is submerged over the entire part in the soln. 3. The electrostatic capacity of the electrode 1 in the air, the electrostatic capacity of the electrode 2 likewise in the air and the specific dielectric constant of the soln. which is unknown or fluctuates are measured and the electrostatic capacity Cx of the electrode 1 is determined. On the other hand, as to the electrostatic capacity Cr of the electrode 2, the electrode 2 is submerged in the liquid and therefore the filling rate is determined as the ratio of the capacity Cx and capacity Cr by which the soln. L is easily calculated.