To realize a color image processing unit that can conduct an excellent smoothing processing not causing color slurring in spite of a simple mechanism.

The color image processing unit is provided with a monocromatic conversion unit 21 that is a color image smoothing processing circuit smoothing color image data formed by combining a plurality of color data per pixel and generates monochromatic image data corresponding to the color image data, with a smoothing discrimination unit 22 that discriminates the necessity of smoothing processing to the monochromatic image data to generate correction data and with color data correction units 24Y, 24M, 24C, 24K that correct a plurality of color data on the basis of the correction data.