In a color conversion characteristic determining method for use with an image display device in which image data is converted on a pixel-by-pixel basis, referring to the color conversion characteristic, and the color-converted image is displayed, a color conversion characteristic candidate is set, and color-converted data are predicted by using input image data, and then tristimulus values of the displayed colors are predicted, and the results are evaluated to judge whether the color conversion characteristic satisfies the requirement. It is possible to make the color conversion characteristic to obtain color reproduction closer to the ideal color reproduction according to a standard, and the color conversion characteristic can be determined in a short time.