In order to implement satisfactory color reproduction which effectively uses the gamut of an output device without causing any tone burning-out in only a specific gamut, a gamut that can attain colorimetrically approximate mapping must be set in consideration of the characteristics of colors and gamuts. Hence, upon converting a first gamut onto a second gamut, a third gamut having a shape according to the characteristics of the color or gamut is set inside the second gamut. The first gamut included in the third gamut is mapped onto the second gamut which is colorimetrical matching or approximate to the first gamut. The first gamut outside the third gamut is mapped onto the second gamut outside the third gamut.