Abstract: An image forming system, for preventing forgery of paper money, a check, securities or the like, having a plurality of copying apparatuses, and a controller, for controlling each of the copying apparatuses, connected with them through a communication line. The copying apparatus includes a reader which reads an image as of the paper money, etc. and which outputs image data corresponding to the image; a printer for printing the image read by the reader on paper; a first transmitter for transmitting the image data to the controller through the communication line; and a prohibiting device for prohibiting an operation of the printer. A signal, which prohibits copying, is transmitted from the controller to the copying apparatus.