To effectively use an image memory both when a color head is mounted and when a monochrome head is mounted by making the maximum memory area for sending images at the time of the color head mounting smaller than the maximum memory area for sending images at the time of the monochrome head mounting.

When one memory shares a memory area for a sending image and a memory area for a receiving image, this device has a means which allocates memory areas for sending images and receiving images and a means which switches a maximum memory area that can be allocated for sending images at the time of allocating a memory area between when a color head is mounted and when a monochrome head is mounted. A maximum memory area for sending images when the color head is mounted is smaller than a maximum memory area for sending images when the monochrome head is mounted. Relating to the device, image memory 105 stores received images, sending images, etc., and an external device I/F part 106 sends and receives data with an external device.