Upon re-creating a conversion table, which is created for each device and viewing conditions, so as to absorb variations of the color reproduction characteristic of a device, data indicating the relationship between color signals on the color space of the device whose color reproduction characteristic has varied, and color signals on a device-independent color space must be obtained again. Hence, input data is converted into output data using conversion tables for input and output conversions, which are created for an input or output device and for each conversion setting, and a conversion adjustment table. The conversion adjustment table is modified in correspondence with variations of the color reproduction characteristic of the input or output device or color correction for the input or output device.