A method of easily obtaining a color conversion matrix serving as a foundation of color reproduction at a high speed irrespective of its degree is provided. The method has: a step of constructing nth-degree matrix coefficients regarding a first color space of a plurality of color patch data sets and obtaining a pseudo inverse matrix to the obtained matrix; and a step of forming a color conversion matrix from a product of a matrix constructed by color data regarding a second color space of the color patch data sets and the pseudo inverse matrix.