To provide an image-processing device having a frame memory for efficiently using a general-purpose memory chip.

The color image-processing device comprises a mode selection section 8 for selecting either a full-color mode or a black-and-white mode, a color conversion circuit for converting the color of RGB data, a compression/ decompression section 5 for compressing color conversion data in 2×2 pixel block units, a selector for selecting compression data or data before compression, a memory control circuit 6 for storing selected data at a frame memory 7, the compression/decompression section 5 for decompressing data read from the frame memory 7, a selector for selecting either the decompression data or data before decompression, and an inverse color conversion circuit for inversely converting the color of the selected data to RGB data. The two selectors select compression and decompression data when the full color mode is selected.