PROBLEM TO BE SOLVED: To provide a system for purifying water quality and bottom sediment of a cultivation and eutrophication water area of Bivalvia, capable of not only rapidly increasing a yield per unit area to stably supply the Bivalvia to a market at low costs but also preventing environmental pollution that is diffusion of ecological pollutant in chemical-type, microbe treatment-type, and physical filtration-type purification systems.SOLUTION: A system for purifying water quality and bottom sediment of a cultivation and eutrophication water area of Bivalvia, includes a cultivation device 1 formed by layering a plurality of plate-like containers 2 each becoming a raising bed for benthic organisms such as a bivalve in the vertical direction, and defining horizontal intervals Dbetween a central hollow 4 penetrating the layered raising beds 2 in the vertical direction and the respective raising beds communicating with the hollow. The cultivation device 1 is immersed into eutrophication polluted water area to bring benthic organisms into a living active state, so that particulate organic matter inside the polluted water is removed by filter feeding properties thereof to purify water quality and bottom sediment.
