PURPOSE: To discriminate on original size and to facilitate trimming by reading and displaying an original image on a display board.

CONSTITUTION: A scanning optical system moves on the reverse surface of platen glass to scan on an original placed on its top surface, and projects its image upon the surface a photosensitive drum. The scanning optical system makes a preliminary scan on the original prior to said exposure process, and the original image is converted into an image electric signal by a solid-state image pickup array inserted into a projection optical path by rotation. This read is executed line by line, and the whole of the read original image is displayed on a liquid-crystal display board 76 through a latch circuit and display device driver. An additional lens is inserted right in front of the solid-state image pickup array on its rotation to eliminate the need to put the array right in front of the exposure area of the photosensitive drum. In practice, the array is set right behind a zoom lens of variable power. The image signal is converted into a binary signal to reduce the necessary memory capacity.