Abstract: First and second original documents are copied on the opposite sides of a copy sheet in superposition in such a manner that the centers of the two copied images on the opposite sides of the copy sheet are coincident with each other. The two copied images are offset from the center of the copy sheet, leaving a blank area at one edge of the copy sheet for binding a number of copy sheets together in book form. The present copying machine is further provided with two sheet cassettes containing copy sheets of different sizes, a device for selecting the desired copy sheet size and intermediate sheet holder for temporarily holding the selected copy sheet between the copy operations of the first and second original documents.