1. A color space transformation matrix calculating method that calculates a color space transformation matrix which transforms colors in a first color space to colors in a second color space, the method comprising: optimizing a plurality of constant color-space transformation matrices, so that each of said constant color-space transformation matrices is adjusted to transform each standard color in said first color space to each goal color in said second color space, which correspond to each said standard color; and calculating interpolation functions for each matrix element of a color-space transformation matrix applied for the entire gamut of said first color space, based on said constant color-space transformation matrices.