PURPOSE: To clean an eutrophicated lake or pond at a low running cost by embedding suction pipes bored with plural holes on the peripheral surfaces into the bottom land of the lake or pond and connecting a drain pipe opened toward the front layer of the like or pond interposed with a drain pump to the suction pipe.

CONSTITUTION: Plural pieces of the suction pipes 2 bored with the plural holes on the circumference are flatly embedded into the bottom land of the eutrophicated lake or pond 1. The drain pipe 3d interposed with the drain pump 30 for lifting the underground water and bored toward the front layer of the lake or pond 1 is connected to the suction pipes 2. Namely, the underground water in the suction pipes 2 is lifted and is discharged toward the surface layer of the lake or pond, by which the eutrophicated lake or pond is cleaned. The driving power of the drain pump relating to this lifting is necessitated merely to accelerate the draining and, therefore, the running cost is reduced. The eutrophicated water is utilized and there is no need for a denitrification tank under the lake bottom. There is no need for the procurement of land and the construction cost is reduced.