To evaluate water pollution with reference to conservation of water resources in rural area, wemeasured electric conductivity and nitrate concentration of surface water at 65 sites in Saijyo basin. In addition,we evaluated the spatial distribution of water pollution, using geographic information on 250m mesh map.Interrelations between the altitude in geographic information and water quality were represented under threeconditions, farmland in land use, lowland in landform and altitude of lower than 300m. On the basis of theserelationships and geographic information, we estimated electric conductivity at the each factor on 250m meshmap. We confirmed the water pollution at the central area of the basin with the estimated 250m mesh map.