To stabilize discharge of a printing paper at first printing.

At first printing, a processing unit 4 processes a stencil base paper S and one sheet of printing paper P is fed from a paper feeding unit 6 while attaching the stencil base paper S to a plate cylinder 28. In this case, a suction fan motor 47 is controlled so as to increase the suction force thereof after the rear end of printing paper P has passed between the plate cylinder 28 and a press roller 29. According to this method, the rear surface of printing paper P can be prevented from being slipped on the paper discharging unit 7 or from generating scratches or creases whereby the stabilized discharging of the paper can be effected.