A printing apparatus which prints the dot-matrix characters or dot-matrix graphic patterns on a paper sheet one page at a time by scanning a photosensitive drum with a modulated laser beam in accordance with the recording data externally supplied and by transferring an image on the drum onto the paper sheet. This printing apparatus comprises page memory for storing the dot-matrix image according to the recording data, margin table for storing the margin data of the respective sizes of the paper sheets and a controller for incorporating the margin data into the dot-matrix image read from the page memory and for supplying the incorporated image to the laser scanning unit for modulating the laser beam.