The history of riverbed estimation using UAV (Drone) has just started. The authors have studied distribution map of vegetation using UAV, investigation of earthquake disaster, estimation of water quality, etc. Recently, making the riverbed area visually by drone would be clearly. In this study, the depth of the river was estimated using DEM (Ministry of Land, Infrastructure and Transport) and DSM (UAV). Phantom 4 Professional was used for UAV. ArcGIS was used for analysis, PhotoScan was used for image combination and creation of 3D model. As a result, the water depth estimation of UAV in the Kounoura River approximately was calculated by subtracting the DEM data and the DSM data using UAV and multiplying by the refractive index of light (1.33). Although the result consideration of this research was calculated one-dimensionally, further effects can be expected by using the three-dimensional method of PhotoScan and ArcGIS.