A system for realizing support of safety driving or automatic driving is provided, in which a vehicle-mounted stereo camera is used to detect obstacles on a road surface such as vehicles going ahead and pedestrians with a high accuracy even in a situation in which a reflected image of an obstacle or a surrounding structure is appeared under a wet road condition in rainy weather. The system includes an image capture section 12 capturing images from two cameras, an image transforming section 14 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 16 detecting a traffic lane on a road on the basis of characteristics of the image obtained from the second camera, a similarity calculating section 18 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 between the first camera's image and the second camera's image and between the second camera's image and the transformed image 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 camera's image and the second camera's image and between the second camera's image and the transformed image, and an obstacle judging section 20 detecting the object from a difference between the two kinds of degrees of similarity on the road region sequentially obtained by the similarity calculating section 18.