1. A colorimetric-data correcting method performed by a computer, the method comprising: printing with a printing device color patches in colors each corresponding to one of a plurality of coordinate points in an output color space defined for the printing device; measuring each printed color patch with a colorimeter to obtain colorimetric data for each printed color patch, the colorimetric data being represented by coordinate data in a device-independent standard color space; correcting with a correcting unit the colorimetric data for each of at least one printed color patch by performing a calculation using at least three (3) colorimetric data including the colorimetric data to be corrected; and creating a look-up table based on the corrected colorimetric data, wherein an input color space for an input device is defined three-dimensionally by three coordinate axes; wherein grid lines are defined in the input color space to form a cube-shaped grid having surfaces, edges, and corners, each grid line extending parallel with one of the three coordinate axes, the grid lines dividing an edge length of the cube shape by an integer N at regular intervals, where the integer N is greater than or equal to two (2); wherein grid points are defined at each intersecting point of the grid lines, each grid point in the input color space having a one-to-one correspondence with each of the plurality of coordinate points in the output color space for representing each patch; and wherein the step of correcting the colorimetric data includes correcting the colorimetric data obtained for the grid points other than the grid points that are positioned at the corners of the cube-shaped grid.