PURPOSE: To always obtain the copied pictures of the optimum characteristics, by measuring the characteristics of a picture to be copied simultaneously with a copying operation and performing the copying operation while adjusting the characteristics.

CONSTITUTION: A control section 31 using a microprocessor which detects the presence/absence of electrostatic charge by inputting potential signals from potential sensors 21 and 22 and outputs control signals to driving motors 27W30 under fixed conditions by inputting the binary detecting signals of potential detecting circuits 25 and 26, etc., operates in accordance with the actuating operation of an operation display section 32. The control section 31 performs copying operations while measuring four characteristics of a leading edge erasing quantity, leading edge resist quantity, longitudinal magnification, and transverse magnification, and, at the same time, when the measured characteristics values are deviated from previously set appropriate values, changes the controlling timing or rotating speeds of each driving motor 27W30 so as to maintain each characteristic value at the appropriate value.