First, a color close to a prediction target color is selected as a similar color from among a plurality of sample colors for which spectral reflectances of a plurality of patches are obtained. Next, for a similar color, a relational equation representing the relationship between the spectral reflectances of a solid patch (a patch with the highest ink density) and the spectral reflectances of a color prediction target patch is obtained. Finally, the spectral reflectances of the solid patch for the prediction target color are applied to the relational equation, by which predicted values of spectral reflectances of the color prediction target patch for the prediction target color are obtained.