Under the conditions that there are 2 or more samples produced in a CCM toning or visual toning process by which colors are adapted to the target color and respective components such as a coloring agent defining the sample color are registered in a CCM system, the reproducibility of the samples is evaluated based on the difference ΔR−n (n denotes a sample number) between spectral reflectance RST−n obtained by actually measuring the respective samples and spectral reflectance RPR−n obtained by the CCM simulation corresponding to the coloring agent recipe for the sample color at the same n, and determination whether toning work should be continued or not is rapidly and simply performed. On the other hand, when an abnormal sample is perceived, the difference ΔR′−b of the sample obtained from the specified equations is determined and, by comparison of the difference between the target color and a color of a toning sample in the color matching process, components such as a coloring agent mixed into the abnormal sample is presumed and its mixed amount is presumed.