An ink supplying unit (34) supplies a water-based ink having a predetermined water content set in advance. An ink form roller (33) receives the water-based ink from the ink supplying unit (34). A plate cylinder (32) is in contact with the ink form roller (33), and receives the water-based ink from the ink form roller (33). A water-content decreasing unit (52) decreases the water content of the water-based ink on the ink form roller (33).
