The analysis of overland flood flow on urban area is generally very expensive and effortful. The aim of this study is to develop an analysis system of processing some data for analyzing overland flood flow and to show the calculated damage situation by means of GIS. In this system, the property data and elevation data for all grids of Cartesian coordinates are easily formed by digital map and GIS. The information on building and population is similarly taken into the system. Moreover, from the comparison with the results of overland flood analysis and the data on the number of houses, population and underground space obtained from digital map and GIS, not only the flood situation but also the damage estimation was easily examined.