There is provided with an image processing device. An obtaining unit is configured to obtain a mixed spectral reflectance of a region in which a first color and a second color are mixed in an image including the first color and the second color, a plurality of first spectral reflectances of the first color, a plurality of first halftone dots associated with respective ones of the plurality of first spectral reflectances, a plurality of second spectral reflectances of the second color, and a plurality of second halftone dots associated with respective ones of the plurality of second spectral reflectances.