PURPOSE: To prevent emulsification induced by excess ink and damping water to obtain a product of high printing quality, by a method wherein needless ink is removed by an ink scraping mechanism brought into contact with an fountain roller supplying the required amount of ink to a printing medium.

CONSTITUTION: The tip end of a scraper 78 is brought into contact with an fountain roller 84 by rotating a lever 72 and securely positioned by a lever 70. Displacement of an arm member 36 in the direction of an arrow A results in rotation of an ink supply member 54 in the direction of an arrow C to provide a fixed gap on a tip end portion 56 thereof. After the positioning is carried out as mentioned above, ink is supplied to the ink supply member 54. Removal of excess ink applied near around the both ends of the fountain roller 84 by using the scraper 78 prevents the excess ink from transferring to a transfer roller 86. Accordingly, as deposit of ink is not occured in a plate cylinder and a rubber cylinder, it is made possible to eliminate troubles such as emulsification of the ink caused by damping water, thus enabling an offset printing machine to perform a satisfactory printing operation.