To prevent a significant impact from being inflicted to an ink fountain roller when an ink duct roller is switched to an ink ducting position.

Plural ink duct rollers 13 are arranged at an interval in the longitudinal direction of an ink fountain roller 3, in proximity to the ink fountain roller 3 of an ink fountain 1, and each of the ink duct rollers 13 is individually switched to an ink ducting position set in contact with the ink fountain roller 3 and an ink-non-ink ducting position remote from the ink fountain roller 3. An ink is ducted by switching the specified ink duct roller 13 to the ink ducting position at a specified ducting interval, and the amount of an ink ducted to the ink duct roller 13 is controlled by controlling the rate of switching frequency to the ink ducting position per duct roller 13. In order to prevent all the ink duct rollers 13 from being switched to the ink ducting position simultaneously, the ink duct rollers 13 are switched to the ink ducting position at mutually different time from each other.