PURPOSE: To separate an area through a simple configuration even in the case that plural color components are combined.

CONSTITUTION: The outputs of representative vector calculating means 10a, 10b express the area to be separated or another area other than it respectively. Discrimination whether a color signal being processed presently is the area to be separated or another area is determined by an area discrimination signal given from the outside. The precision of this area discrimination signal is rough compared with the precision of the area to be separated. A representative vector is the central value of each area, and the difference of the representative vectors calculated by the representative vector calculating means 10a, 10b is calculated by a color axis calculating means 11, and the direction of a difference vector is determined. A color mapping means 12 executes the mapping of the color signal to the direction calculated by the color axis calculating means 11. The highly precise area dividing of the color signal mapped to one-dimensional space by the mapping means 12 is executed by an area judging means 13. The input component of this area dividing is one-dimensional, and can be constituted comparatively easily by using a histogram, etc.