To shorten processing time without lowering image quality.

RGB color system data of which the color matching processing is performed is converted into YUV color system data and outputted to an image processing part 15 by a color converting part 14. Resolution is raised so that the resolution of the inputted YUV color system data becomes equivalent to printing resolution, in this case, a curved surface interpolation processing is performed for a Y plane, a linear interpolation processing is performed for a U plane and a closest processing is performed for a V plane by the image processing part 15. Thus, since a highly accurate processing is performed for the Y plane by which visual sense of a man is affected most, no image quality in appearance is lowered. In addition, since simple image processings are performed for the U, V planes, the processing time as the whole is shortened while maintaining the image quality.