1. A color conversion table generation method comprising: generating a first color conversion table by estimating device colors corresponding to colors of grid points of the first color conversion table from colorimetric values obtained by colorimetrically measuring colors of a gamut reproduced by an output device; generating a second color conversion table in which the number of grid points is more than the number of the grid points of the first color conversion table by estimating device colors corresponding to colors of the grid points of the second color conversion table from the colorimetric values obtained by colorimetrically measuring the colors of the gamut reproduced by the output device; interpolating the colors between the grid points of the first color conversion table to obtain interpolated colors corresponding to the colors of the grid points which are included in the second color conversion table and are not included in the first color conversion table; and correcting the first color conversion table by changing the colors of the grid points of the first color conversion table such that the interpolated colors approach to the colors of the grid points included in the second color conversion table.