To reduce an error in measurement for a subject with repetitive patterns, by placing second and third cameras constituting a stereo image pair at different distances to form a plane around a first camera.

A standard camera 3 inputs at least one of photographed images as a standard image, while a reference camera 4 inputs at least one of photographed images as a reference image. A corresponding pixel determining means of a CPU determines a pixel on the reference image input by the camera 4 (4-1 to 4-4) corresponding to a predetermined pixel on the standard image input by the standard camera 3 and calculates the distance from a standard point to an object point by a distance calculation means using parallax corresponding to the determined pixel. The standard camera 3 is located at the center, the reference camera 4-1 is located at a distance L3 on upper left from the center, a reference camera 4-2 is located at a distance L4 on upper right from the center, a reference camera 4-3 is located at a distance L3 on lower right from the center, and the reference camera 4-4 is located at a distance L4 on lower left from the center, wherein three of them are combined.