1. A method for verifying a color matching precision, comprising the steps of: (a) determining, in a device-independent color space, a relationship in a magnitude of a distance X between an achromatic color point indicating an achromatic color and a new target color gamut point on a boundary of a new target color gamut for which color matching precision is newly verified, a distance A between said achromatic color point and a verified target color gamut point on a boundary of a verified target color gamut, for which color matching precision has already been verified, and having a same hue as said new target color gamut point, and a distance B between said achromatic color point and a printer color gamut point on a boundary of a printer color gamut, with which an image can be formed by a printer, and having the same hue as said new target color gamut point; (b) in a case where said distance X is determined to be more than said distance A and said distance B is determined to be less than said distance A and said distance X in said step (a), calculating said new target color gamut point having the same hue as said verified target color gamut point; and (c) calculating, as the color matching precision of said new target color gamut point, a color difference between said new target color gamut point calculated in said step (b) and a measured color value of an output given by said printer for said verified target color gamut point.