1. A color image data correcting method for producing a color correction table for correcting multiple gradation color image data in order to correct color drifts in the printed results by printing devices and for correcting the color image data by means of the color correction table, the method comprising: printing predetermined color patches on the basis of patch image data for printing a plurality of patches of which color gradation values have been changed for each color of each color material for recording used in the printing devices; acquiring the color values of the color patches by measuring the color of the printed color patches; interpolating the color values corresponding to all the color gradation values of the color correction table by referring the color values acquired and by using a predetermined function; and contrasting the color values corresponding to all the color gradation values acquired by the interpolation and the standard values that are the color values of the standard printed results, and on the basis of the contrast result, producing a color correcting table for correcting the color image data so that printed results equivalent to the standard printed results corresponding to the color image data of any color gradation values may be acquired by the printing devices, wherein, in interpolating and obtaining color values, a predetermined higher degree polynomial expression having the color gradation value is selected as a variable by referring to the color value acquired, and the higher degree polynomial expression is used to interpolate color values corresponding to all the color gradation values, and wherein, in interpolating and obtaining color values, deviated values formed at coordinates in the predetermined direction from the assumed interpolated curve in the predetermined color space among the color values interpolated by the higher degree polynomial expression are detected, and color values are interpolated by switching over from the higher degree polynomial expression to interpolating calculations unlikely to result in deviated points in color gradation regions where the deviated points are detected.