An apparatus includes an image processing circuit to perform quantizing processing of image data, which has a plurality of rasters, each of which is formed with a plurality of pixels, by an error diffusion method, to generate print data. The image processing circuit is capable of performing quantizing processing of image data for N colors, and performs the quantizing processing multiple times in image processing of image data for colors more than N colors. In a case when the image processing circuit performs image processing for image data for colors more than the N colors, the image processing circuit repeatedly performs at least first image processing for performing image processing of image data of a first color group and second image processing for performing image processing of image data of a second color group for each band.