A variable magnification electrostatic copying apparatus includes a stationary transparent plate for placing thereon a document to be copied, an optical system including a first reflecting mirror assembly adapted to be moved reciprocally along the transparent plate, a second reflecting mirror assembly adapted to be moved reciprocally at a speed equal to one-half of the moving speed of the first reflecting mirror assembly and a lens assembly to be held at any one of a plurality of positions corresponding to a plurality of projecting ratios, and a projecting ratio changing device for moving the lens assembly and the second reflecting mirror assembly so as to change the projecting ratio of the optical system. The projecting ratio changing device includes a drive source in the form of a stepping motor, a control for controlling the operation of the drive source, a setting member for moving the second reflecting mirror assembly, a first power transmission system interposed between the drive source and the setting member and a second power transmission system interposed between the drive source and the lens assembly. The second reflecting mirror assembly is moved through the first power transmission system and the setting member, and the lens assembly is moved through the second power transmission system. An exposure correcting device includes plural plates movable between non-operating positions to respective operating positions controlling the area of exposure. The control includes high and low speed rotating plates and optical detectors for detecting positions thereof and for controlling the stepping motor.