A copying machine is configured to execute a first scanning process to scan an image on an original sheet and generate image data, which is stored in a storage of the copying machine and an external processing device, a printing process to print the image of the original sheet, a second scanning process to release an image data storing area of the storage, and store the image data in the storage and the external processing device, a transmission process to release the image data storing area of the storage, and transmit the image data from the external processing device to the storage, and a detection process to detect whether a free capacity of the storage becomes less than a particular value.