In FIG. 4, the image memory unit 3 writes the binary image data sent from the external interface process unit 4 and the image process unit 170 into a page memory 301 composed of a memory such as a DRAM and the like through a memory controller unit 302, reads and sends the image data to the printer unit 2, and accesses image data input/output to/from a hard disk 304 being a large-capacity memory.