In recent years, it is concerned the eutrophication by nitrogen or phosphorus in the closed water area like the developed bay area, the inland sea or the lake as one of water pollution problems. For such problems, it is necessary to argue not only about removing pollutants but also about regulatory of inflow pollutants and problems of cost burden. In this paper, we built the spatial economic model based on the concept of general equilibrium theory to evaluate the water quality improvement policy. The model is focused on agent s activities with drawing and exhausting water, and cleared the incidence relationship of benefits/costs among agents by the benefit incidence table. We examined effects or influences of water pricing to improve pollutants.
