To contrive to improve the working efficiency in a stage changing and that in the cleaning after the finish of printing by a method wherein a plate cylinder is driven at its cleaning position and, at the same time, the cleaning of the plate cylinder and a cascade is carried out by supplying a cleaning solvent to the cascade.

By changing-over an ink dupply with the changing-over means of an ink supplying means N after the finish of one printing, a cleaning solvent is supplied to a cascade 50 at a printing position P so as to pre-clean a plate cylinder 3 and an ink roller 46 under driving state. By this pre-cleaning, the cylinder and sealing means of the ink supplying means N and a doctor are cleaned and, at the same time, the ink adhering to the plate cylinder 3 and the ink roller 46 is prevented from being dried during its movement to a cleaning position. As a result, a cleaning process can be carried out even during printing at the printing position and, at the same time, a cleaning is carried out by driving the ink roller 46 with a cleaning driving means, resulting in allowing to improve a cleaning capability.