PURPOSE: To vary a print color and a display color in response to each purpose by inputting a display color signal seeming like a print color sample and preparing a look-up table LUT making the print color coincident with the display color.

CONSTITUTION: A sample #1 is prepared for a prepared for a print color sample 9 that is printed under the conditions same as those where the images stored in an image data storage 1 are printed later by a printer 4. Then the color signal value is written in a color signal table 6 by a print color signal value input device 10. A color signal generating device 5 is controlled so that a color most apporximate to the sample 9 is shown on a display device 3, and the output registered in the table 6 as the color signal value #1. Then the color signal value of #2 is registered in the same way. The degree of coincidence of an LUT 2 is improved as the number of preceding jobs is increased. As a result, the information registered in the table 6 shows the characteristic of the color signal conversion to be carried out by the LUT 2. The coordinates showing these colors are evenly distributed in an input value space, and the input value of colors included in the entire value space can be generated from those even information through the interpolation.