PURPOSE: To prevent excessive reduction by setting a magnification by supposing that with regard to the size of a copying paper, the length is a width of the copying paper, and the width is a length which has subtracted a biding margin from a length of the copying paper, in case of combining a binding margin reduction copy mode and an automatic magnification setting function.

CONSTITUTION: A start button 50 of an operating panel is pushed, and a binding margin copy mode is selected by a key 82. When a manual feed door is closed, a binding margin + an automatic reduction copy mode is set, and a pilot lamp 144 is turned on. Also, by keys 67W70, two stages of unmagnification and fixed reduction, and one stage of fixed magnification are set automatically. The size of a copying paper is detected by a paper feed port, the upper feed paper and the lower feed paper are displayed by turning on an indicator 130 and an indicator 131, respectively, and the size of the copying paper is derived. As for the size of the copying paper, it is supposed that a width of the copying paper is its length, and the length which has subtracted a binding margin from the length of the copying paper is its width, and from the size of an original, a reducing magnification is calculated and derived automatically by a CPU. In such a way, a detect and the excessive reduction of an image can be prevented.