To provide a zone discrimination device and a method and program of zone discrimination with which clustering processing for intensity of each color is performed and the respective zones of foreground zone, background zone and noise zone can be discriminated with accuracy.

A zone discrimination device includes an input part 14 for inputting a plurality of images on which the same object is displayed with a sole color and a control part 11 for performing clustering processing based on mixed normal distribution model for images input with respect to each color and assigning the pixels of the images to one of a foreground zone, a background zone and a noise zone.