PURPOSE: To perform an image arithmetic processing at a high speed in the case of searching which part in one image includes a correspondent point included in the other image.

CONSTITUTION: An object 3 is photographed by two cameras 2-1 and 2-2, while paying attention on a reference plane 1 such as a floor on which the object 3 is arranged, for example, a search area is set within the range of a fixed elevation angle α watched from the cameras. The image of this search area 5 is projected in the shape of a band at one part of images 4-1 and 4-2 of the cameras. A correspondent point 6 of the object 3 included in one image 4-1 is included in the search area 5 of the other image 4-2. Therefore, image processing for searching the correspondent point is performed within the range of this search area 5. Thus, an image arithmetic processing range is limited and the time for processing is shortened.