To precisely adjust height of a submerged pump so as to prevent the submerged pump from being embedded in sedimentation deposit.

A submerged pump main body 11 is floatedly supported on a water level WS while a suction port 11b is sunk in the water by means of a metal can 12, for discharging supernatant water W. Since a suction hose 14 extended from a discharge port 11b of the submerged pump main body 11 has flexibility, this water level following submerged pump 1 is lowered while following up lowering the water level due to discharging accompanied with flexible deformation of the suction hose 14. When the metal can 12 is seated on sedimentary deposit D, the suction port 11b of the submerged pump main body 11 is located higher than the deposit D. The deposit is not discharged together with the water, accordingly. After the metal can 12 is seated at the deposit D and a draft line DL is lowered to a position of a float switch 13 or lower, the submerged pump main body 11 is stopped by the float switch 13.