To reduce a loss in a high speed range where a printing machine sound is high without giving a discomfort to an operator by controlling the relationship between a carrier frequency of a PWM inverter for driving a motor and a frequency of an output to a specific value between speeds at the times of printing and cleaning rolls.

The PWM inverter for driving a motor 6 mechanically coupled to rolls of a printing machine 8 is controlled even at the time of cleaning rolls by bringing the rolls into contact with a cleaning implement and rotating the rolls at a low speed in addition to the time of printing. Here, the relationship between a carrier frequency Fch of the inverter and an output frequency (f) of the inverter is controlled between speeds at the times of printing and roll cleaning so that a product of the N-th power (N=0.8 to 2.2) of the carrier frequency Fch and the output frequency (f) becomes a predetermined value. That is, the motor 6 is controlled by a speed control vector control inverter to be controlled by a controller 9.