1. A vehicle-surroundings monitoring apparatus which is mounted on a vehicle for monitoring nearby objects lying therearound, said apparatus comprising: sensing means including two optical systems for sensing said objects lying around said vehicle from two different points and forming images of said objects on image sensor means; display means for displaying images of said objects on a screen; window setting means for setting a plurality of windows on the screen of said display means; distance detecting means for detecting the distance to each object in each of said windows based on the principles of trigonometry by detecting a deviation between images of each object sensed by said two optical systems through comparison therebetween; and detecting range .restricting means for restricting a distance detecting range for each window to a predetermined range to thereby select as a nearby vehicle an object to which the distance is within the predetermined range.