1. A ranging apparatus which determines distances to objects by using planar positions of said objects in images which are obtained by plural image acquiring means comprising: plural cameras that function as said plural image acquiring means, plural distortion correction means to correct distortion of images taken by said cameras wherein said plural distortion correction means progressively determine ranging distances of a target object, a corrective computation means which generates corrected images by using said distortion correction means, being corrected for eliminating distortion caused by optical systems used for said cameras, corresponding to said progressively determined ranging distances in which said images are taken by said image acquiring means, a corrected image selection means which selects a most appropriately corrected image among said corrected images and; a ranging computation means which computes a distance to said object viewed in said corrected image selected by said corrected image selection means.