An image processing apparatus allows a printer to output chart data of a plurality of kinds of color mixture expressed by a three-dimensional color space constructed by CMY; obtains colorimetry values obtained from the output chart data; forms a reference value by converting patch data of the color mixture expressed by the three-dimensional color space into a device independent color space on the basis of a first color conversion table for converting the three-dimensional color space into the device independent color space; corrects a second color conversion table by using the obtained colorimetry values, the formed reference value, and the second color conversion table for converting the device independent color space into the three-dimensional color space; and forms a color conversion table for correcting a four-dimensional color space constructed by CMYK by using the first color conversion table and the second color conversion table.