PURPOSE: To add a display means to display out image information and to reduce the cost and to make a device small-sized by constituting the device so that a storage means for image formation is used as an image display memory in a color copying machine.

CONSTITUTION: In case of correction or addition of copy image, a CRT display mode is designated on a keyboard 56 of a CRT display device 55, and a copy key on an operation panel 2 is depressed, and then, a storage part 68 for image formation is used for not only storage of picture information after color conversion in a color converting part 64 but also temporary storage of image information before color conversion. Since image information read from an original can be displayed out even if the CRT display device 55 is added, correction using the CRT display device 55 is possible.