PURPOSE: To stabilize printing paper on a pressure cylinder and to improve the accuracy of quality inspection of printing by operating the paper pushing range for the printing paper in correspondence with the size of the paper, feeding air into an air nozzle based on the result of the operation, and pushing the printing paper on the pressure cylinder.

CONSTITUTION: A paper-size-preset controlling device 12 sets the size of printing paper in use and outputs the paper size data to an operating device 13. An operating device 13 operates the paper pushing range for the printing paper on a pressure cylinder 3 based on the pulses from a rotary encoder 11 and the paper size data. An air controlling device 16 has a rotary valve 18 and a servomotor 19 which are provided between a blower 14 and an air nozzle 15. The servomotor 19 is driven within the paper pushing range of the printing paper on the pressure cylinder 3 based on the result of the operation of the operating device 13. The feeding of air to the air nozzle 15 from the blower 14 and the stopping of the air are performed by the driving of the servomotor 19. Thus, the printing paper is brought into tight contact with the pressure cylinder, the printing paper is stabilized and the accuracy in quality inspection of printing is improved.