In gamut mapping, when saturation is linearly compressed, a saturation drop of a low-saturation part is considerable. Linear compression based on zone division produces discontinuous points. Nonlinear compression cannot automatically and uniquely calculate a conversion curve. To combat these problems, first and second gamut data are obtained, the lightness ranges of the gamut data are normalized, and the lightness, hue, and saturation values of a sample point of the first gamut data after normalization are calculated. Maximum saturation points which have lightness and hue values equal to those of the sample points are calculated from the first and second gamut data after normalization. A color conversion table is then generated by calculating a mapping point in the second color gamut after normalization, which corresponds to the sample point, on the basis of the saturation values of the maximum saturation points and sample point.