To efficiently perform additional copying without providing a particular configuration in an image forming device.

In the image forming device, when start of a copying operation is instructed, under control of a control part 11, images of an original bundle disposed in an original set position are successively read by a reading part 13 and stored in a memory 14f, and a copy job is generated. After the lapse of a predetermined time from the completion of copying based on the copy job, image data are erased from the memory 14f. Even without the lapse of the predetermined time from the completion of the copy job, when start of a copying operation of the next original bundle is instructed, the image data are erased. Otherwise, the image data are held in the memory, and when additional copying is instructed, copying is carried out again.