1. A driving environment surveillance apparatus comprising: an obstacle detecting unit for scanning a plurality of divided peripheral regions in a travelling direction of a vehicle so as to, if an obstacle is present in said peripheral regions, detect a relative distance and an azimuth to said obstacle from said vehicle; an image detecting unit for detecting two-dimensional images in said peripheral regions; an image processing region limiting unit for specifying a region where an obstacle is present depending upon said azimuth detected by said obstacle detecting unit so as to derive a two-dimensional image corresponding to said specified region from said image detecting unit; an obstacle extracting unit for extracting said obstacle from said two-dimensional image derived by said image processing region limiting unit so as to calculate a size index of said obstacle; and a driving environment output unit for specifying a position where said obstacle is present in a real spacial coordinate with respect to a driving road of said vehicle depending upon said distance and said azimuth detected by said obstacle detecting unit so as to display a figure indicating said size index of said obstacle at said specified position.