PURPOSE: To enable the image of the same density as that at the unmagnification to be obtained even when the magnification is varied, by forming latent images after controlling the charge amounts of chargers in such a manner that the surface potential of an image forming body assumes the same potential as that at the unmagnification when the mangnification is varied.

CONSTITUTION: In a variable magnification device which carries out cpoying at variable magnification from reduction to enlargement by moving a lens 11 to positions 11a, 11b, the position of the lens 11 is changed by a magnification change command, after which an original lighting lamp 6 is lighted to form the surface potential corresponding to the bright part on an image forming body while said body 1 is being charged by chargers 2, 3. This surface potential is detected with a potential sensor 5, and the charge amount is so controlled as to attain the target value. Upon ending of this charge potential controlling, the lamp 6 held integrally with an original lighting mirror 9 is lighted and is moved in an arrow direction to lead the light reflected from the original surface to an imaging part 13, whereby the required latent image is formed on the image forming body.