1. A vehicle surroundings monitoring device comprising: a position mapping unit that carries out a position mapping process of expressing a positional relationship in a detection range in surroundings of a vehicle of a distance sensor that detects an obstacle by coordinates on a camera image captured by a camera having an image capture range in said surroundings of the vehicle; a mapping transformer that derives transformation parameters used for carrying out a mapping transformation in such a way that said obstacle detected by said distance sensor is placed at a predetermined position on said camera image on which the position mapping process has been carried out by said position mapping unit; a camera image transformer that carries out an image transformation on said camera image by using the transformation parameters acquired by said mapping transformer in such a way that said obstacle is placed at said predetermined position; an extra-position-mapping determination unit that determines that an obstacle is not existing in said camera image on which the position mapping process has been carried out and the obstacle is existing in the detection range by said position mapping unit; and a guidance processor that provides guidance showing that the obstacle is existing out of said camera image based on a determination of the extra-position-mapping determination unit.