In this paper, the authors propose a cell-based distributed runoff model using raster spatial data such as digital elevation models (DEM) and remote sensing images. This paper also describes how the hydrograph simulated by the runoff model changes as the spatial resolution of the raster data becomes coarser. The study area is the Yada River basin (110 km2) in the Shonai River drainage system. The runoff model is evaluated using raster data with 50-m resolution and 250-m resolution. Consequently, the hydrographs simulated by the runoff model with 50-m resolution are not sensitive to the model parameters valuesthan those with 250-m resolution.