To perform multicolor printing at a material cost lower than that required for process color when the cost for the multicolor printing is lower than that for the process color.

When a mode other than high-quality mode is specified in a mode specification part 1, a separation method determination part 2 refers to a profile storage part 3 to calculate color material cost for CMYK data and color material cost for CMYKα data containing characteristics α, and determines the CMYK data or the CMYKα data that requires lower color material cost. A color conversion part 4 refers to the profile storage part 3 to convert input image data to the determined CMYK data or the CMYKα data.