PURPOSE: To provide the device which has superior noise resistance and division precision as to a device which divides a two-dimensional image, obtained by photographing a three-dimensional moving body, into areas.

CONSTITUTION: This device has a three-dimensional speed vector calculating means 10, a means 12 which divides the two-dimensional image gradually into small areas, and a means 14 which puts excessively divided areas together; and the means 12 includes a means 16 which calculates a depth value from a three-dimensional speed vector, a means 18 which tentatively divides the two-dimensional image into small areas, a means 20 which finds a body plane as to each area before and after tentative division from the depth value, a difference calculating means 22 for the depth value, a means 24 for finding the decrease rate of the difference, and a means 26 which allows the tentative division when the difference decrease rate exceeds a reference value and the means 14, on the other hand, includes a means 28 which selects a couple of adjacent areas, a means 30 which judges whether both areas are on the same plane or not from an optical flow, and a means 32 which couples both the areas when they are on the same plane.