PURPOSE: To separate ink from moisture and eliminate insufficient ink transfer between rollers to stabilize printing quality by rotating a moisture separation roller at a circumferential speed different from that of a fountain roller.

CONSTITUTION: The titled rotary press scratches residual ink together with residual wetting water after being supplied to a printing plate from a printing roller unit with a wetting water device 16W20 using a blade 8, and recovers the scratched ink into an ink tank 11. A moisture separation roller 30 is driven to rotate at a prearranged circumferential speed which is different from that of a fountain roller 7 in close contact with the latter. For this reason, a moisture-containing ink receives shear effect by the different circumferential rotary speeds between both rollers to separated up into ink and moisture 6'. The ink after moisture separation is transferred to the roller 7 and then to a delivery roller 6, doctor roller 5 and ink application rollers 4a, 4b in that order. After this, the ink is finally supplied to a printing plate 3. Consequently, the moisture contained in the ink to be supplied for printing is stabilized to such an extent that an increase in the moisture content is only equivalent to an added amount of wetting water 6 by the wetting water device, thus preventing an increase in the moisture content of ink (a) in the ink tank 11.