PURPOSE: To prevent the generation of spoilage due to the divergence of printing position when printed additionally, by a method wherein the correction angle is computed from the correlation between the detection signal by a scanning head and the detection signal by an encoder unit and a plate cylinder is rotated by driving a correction drive motor.

CONSTITUTION: The scanning head 9 which detects the mark formed on a plate cylinder 1 and the encoder unit 8 which detects the rotary position of plate cylinder, are provided. A correction drive motor 11 calibrates rotary speed by operating a differential gear mechanism 5 and regulates the positional divergence between the plate cylinder 1 and a matter to be printed. Before exchanging plates, the output value of the encoder unit 8 when the press is stopped, is previously memorized and the plate cylinder 1 is rotated by energizing a correction drive motor 11 leaving a drive motor 4 as it is stopped. Then, the correlation between the detection signal by the scanning head 9 after exchanging the plates and the output value of the encoder unit 8, is obtained. Concerning the correction angle computed on the basis of this correlation, the plate cylinder 1 is rotated with the correction drive motor 11 so that the output value of the encoder unit 8 becomes the memorized value.