Seoul Metropolitan Government(SMG) as well as the other local governments should have a role in managing groundwater according to the Groundwater Law. As a guidance of the management and control of groundwater use, this study emphasizes the necessity of the construction of 1 ; 5,000 hydrogeological maps and proposes possble usages of the maps. As expected to be a part of the groundwater GIS database constructed by SMG, the maps can be used as base maps to facilitate the whole processes related to the groundwater development and preservation. For the purpose of the construction of the 1 ; 5,000 hydrogelogical GIS database, we develop the classification system of the hydro-geological entities and their attributes.