PURPOSE: To execute easily switching of a copying magnification without making a device large in scale by moving an optical system in the vertical direction against an original surface, and forming an image at different position on a paper feed route having a prescribed inclination against its vertical direction.

CONSTITUTION: An optical housing 1 to which a lens 2 and a reflection mirror 3 are fixed can move in the vertical direction against an original surface 22, and an exposing surface 5 is inclined at a prescribed angle determined by a combination of magnification against the vertical surface. A copying paper 9 fed by a carrying belt 12 stops at an exposing position 6 or 7 in accordance with a selected magnification and receives an exposure. When the optical housing 1 moves, a distance between the original surface 22, the lens 2 and the image forming surface is varied, and a variable power is realized by inclining the exposing surface 5 so as to satisfy an image forming condition in each magnification. Accordingly, a copying magnification can be switched easily without making a device a large scale.