Color reproducibility needs to be evaluated in consideration of the influence of homogeneity in page image. Hence, a first chart is formed from an image of a uniform density of a region to be evaluated, and data associated with the spectral reflectances of plural points on the first chart are input. Based on the data obtained from the first chart, color differences between a predetermined point and other points on the first chart are calculated. When the calculated color differences fall within a permissible range of heterogeneity of colors in the region, a second chart is formed from an image corresponding to a color target, and data associated with the spectral reflectances of plural points on the second chart are input. Color differences are calculated from the data obtained from the second chart and data associated with the spectral reflectance of the color target.