PURPOSE: To raise the quality of printing by keeping the emulsifying condition and fluidizing characteristics of ink to be transferred to a plate cylinder by a method in which water present in residual emulsified ink on a doctor roller is separated by shearing forces and the water so separated on the ink film is sucked and removed by vacuum pressures.

CONSTITUTION: Ink carried through each roller from an ink pot 1 to a doctor roller 4 is emulsified with damping water supplied from a watering roller 6 and then transferred to an inking roller 7. Untransferred ink is, however, left on the roller 4 and moved to an oil-water separation blade 11. When the ink comes into contact with the blade 11, a shearing force acts on the ink film to separate water present in the emulsified ink in the form of droplets, and also the water so separated is sucked through a sucking nozzle 12 by a vacuum pump 13 and removed.