PURPOSE: To perform multi-color printing under the discrete and synchronous control of printing units using plate cylinders of different peripheral lengths by a method wherein a servo motor and a servo motor driver are provided for every printing unit, and the servo motor is independently driven.

CONSTITUTION: A plate cylinder rotating speed arithmetic unit 5 for a first-color printing unit calculates a plate cylinder rotating speed command signal in accordance with a speed reference command signal and a plate cylinder peripheral length signal issued from a plate cylinder peripheral length set device 6, and inputs it to a servo motor driver PD1 to drive a servo motor M1. A pulse generated from a pulse tachogenerator PG1 connected to the servo motor M1 is inputted to a second-color servo motor driver PD2 as a speed reference pulse to control the speed of a servo motor M2. The speed is synchronized so that the peripheral speed of a second color plate cylinder R2 is equal to that of a first-color plate cylinder R1 as a reference. A pulse outputted from a second- color pulse tachogenerator PG2 is transmitted to a driver PD3. The speed is synchronized so that the peripheral speed of a third-color plate cylinder R3 is equal to that of the second-color plate cylinder R2.