PROBLEM TO BE SOLVED: To provide a liquid level adjustment device 1 in which the number of liquid surface sensors is reduced by disposing the liquid surface sensors to be movable to an upper part U side and a lower part D side in a longitudinal direction L of a chamber and that automatically performs liquid level adjustment.SOLUTION: A liquid level adjustment device has: a chamber 2 a light emitting and receiving unit 3 liquid surface sensors LS an opening and closing unit OPC a pressure suction unit PV a liquid surface sensor drive unit DV and a control unit CS. The liquid surface sensors LS are mounted to a liquid surface sensor mounting unit 11 arranged at a light emitting and receiving unit 3 side in a longitudinal direction L of the chamber 2 so as to be movable to an upper part U side and a lower part D side. The control unit CS performs interlocking control of the liquid surface sensors LS, the opening and closing unit OPC, the pressure suction unit PV, and the liquid surface sensor drive unit DV, to automatically control a liquid level of the chamber 2 at a proper level.
