The present invention provides an image forming system in which an image of a document can always be printed in an appropriate position of paper with reliability even when a scanning magnification of the image is changed. The system therefore includes a scanner for scanning a document image to generate an image signal, a printer for forming a copying image on paper in response to the image signal supplied from the scanner, a paper feeding section for feeding the paper to the printer, a magnification setting section for setting a scanning magnification when the scanner scans the document image, and a timing control section for controlling timing of supply of the image signal from the scanner to the printer and/or timing of supply of the paper from the paper feeding section to the printer such that the size of a margin between the leading edge of the paper and that of the copying image formed on the paper is fixed irrespective of the scanning magnification.