PURPOSE: To eliminate unevenness in a water film, by arranging a grooved cam at the support shaft of a chromium roller to feed water to an ink-applying roller, and oscillating the roller, being rotated, along its axial direction by the engagement of the grooved cam with a cam follower projected on the roller.

CONSTITUTION: A chromium roller 4 to supply dampening water from a water source roller 5 is in contact with an ink-applying roller 3 which applies blended ink to the form plate 1' of a printing drum 1 with a swing roller 2. The chromium roller 4 is pivoted to a support shaft 9 fixed to frames 8, 8' by bearings 11, 11' of a roller main body 10. A gear 12 fixed to the bearing 11 engages with the gear 13 of the water source roller 5 and drives the roller 10. In this case, a grooved cam 14 is formed at the support shaft 9, and its cam groove 15 is engaged with a cam follower 17 projected from the bearing 11. Thus, the support shaft 9 is rotated so that the chromium roller 4 axially oscillates during its rotation.