Upon generating a look-up table data used to retouch and color-convert arbitrary image data imaged by an imaging apparatus, when the saturation value of source image data is equal to or smaller than a predetermined threshold value, new image data which undergoes tinting correction of achromatic colors by multiplying the saturation value of the retouched image data by a correction coefficient calculated from the saturation values of the source image data and retouched image data is generated. Then, a look-up table is generated using the source image data and the new third image data which is free from any tinting of achromatic colors. Upon generating a look-up table for color conversion, new image data which undergoes tinting correction of achromatic colors by converting grid point storage values stored at grid points representing achromatic colors of a basic look-up table into achromatic color data is generated, and a look-up table is generated using the source data and the new image data which is free from any tinting of achromatic colors.