PURPOSE: To improve safety for forgery by allowing one piece of blanket cylinder selected from at least two pieces thereof to interact with at least one piece of an additional printing device and bringing a plate cylinder contained therein into contact with the respective blanket cylinders.

CONSTITUTION: A paper 1 is supplied in a state of a sheet and a multicolor rotary printing machine has a stationary cylinder 2, a transfer cylinders 3 provided with grippers and a feed device equipped with dirt sweeping and static eliminators 3' arranged on both sides of the paper 1. The sheet is transferred on a blanket cylinder 4 interacting with other blanket cylinder 14 which equips the gripper and has the same diameter as the blanket cylinder 4. The sheet is passed between two pieces of blanket cylinders 4, 14 and thereby simultaneous printing is performed on both sides. These cylinders are rotated in the direction shown by arrows. After printing, the sheet is transferred to a heap of fed-out paper or favorably transferred to a machine finishing printing by a chain gripper mechanism 24. The blanket cylinders 4, 14 come into contact with plate cylinders 5, 15 which are arranged in the lower peripheral area and carry gathering printing plates 5a, 15a of a typographic printing form plate type.