A system for realizing support of safety driving or automatic driving, in which a vehicle-mounted stereo camera is used to detect obstacles on a road surface even in the presence of a reflected image of an obstacle under a wet road condition. The system includes two cameras, an image transforming section transforming a first camera's image by image transform T that transforms any given pixel in a road surface region in the first camera's image to a corresponding pixel in a second camera's image, a lane detecting section detecting a traffic lane on a road on the basis of characteristics of the image obtained from the second camera, a similarity calculating section sequentially establishing processing regions, each having a base formed by one of image lines in a region within a lane, for carrying out inter-image arithmetic operations on the assumption that an obstacle stands from a contact line on a road surface as an image line, and obtaining respective degrees of similarity between the first cameras s image and the second camera's image and between the second camera's image and the transformed image, and an obstacle judging section detecting the object from a difference between the two kinds of degrees of similarity on the road region sequentially obtained.