1. A color conversion definition creating method of creating a color conversion definition defining a relation of data conversion between RGB data representative of a combination of values of R, G and B for a printer and CMYK data representative of a combination of values of C, M, Y and K for printing to perform printing in which a color of an image outputted by a printer receiving the RGB data and outputting the image is reproduced, said color conversion definition creating method comprising: a first conversion step of converting RGB data for a printer into calorimetric data of device non-dependence in accordance with a printer profile representative of color reproduction characteristic of the printer; a second conversion step of converting the calorimetric data determined in said first conversion step into CMY data representative of a combination of values of C, M and Y; a first K-function creating step of setting up a first color conversion parameter and determines a first function of K from CMY data of C&equals;M&equals;Y of CMY data determined in said second conversion step in accordance with a data conversion algorithm for converting the CMY data into CMYK data having a printing aptitude according to the first color conversion parameter set up; a first association creating step of determining CMYK data bound by the first function of K determined in said first K-function creating step, associated with the same calorimetric data as the calorimetric data associated with CMY data of C&equals;M&equals;Y of the CMY data determined in said second conversion step, in accordance with a printing profile representative of color reproduction characteristic of printing, so that a first association for providing an association between the CMY data of C&equals;M&equals;Y and the CMYK data is determined; a second K-function creating step of setting up a second color conversion parameter value based on the first association determined in said first association creating step instead of the first color conversion parameter, on the data conversion algorithm, and determining a second function of K over an arbitrary combination of C, M and Y from the CMY data determined in said second conversion step, in accordance with the data conversion algorithm on which the second color conversion parameter value is set up; and a second association creating step of determining CMYK data bound by the second function of K determined in said second K-function creating step, associated with the same calorimetric data as the calorimetric data associated with an arbitrary combination of C, M and Y of the CMY data determined in said second conversion step, in accordance with the printing profile, so that a second association for providing an association between the arbitrary combination of C, M and Y of the CMY data and the CMYK data is determined.