To provide a pond purification device for purifying the water quality of a pond.

The pond purification device comprises a water intake port 5 located in the deep part of a pond a suction line 3 connected from the water intake port 5 to a pump P, a feed pipe 4 for supplying water (a chemical liquid) supplied from the pump P uniformly throughout the pond, a number of connecting pipes 9 connected to the feed pipe 4 at regular intervals so as to be branched from the feed pipe 4 toward the pond, venturi nozzles each of which is connected to the tip end of the connecting pipe 9, and the middle of which is connected with a suction pipe communicating with atmosphere. Pond water is injected from the venturi nozzles. The pond water supplied from the pump P is injected into the pond so that the injected pond water is quickly returned to the water intake port 5, thereby increasing dissolved oxygen in the pond.