To provide a method for adjusting damping water supply by which paper spoilage at the start of operation can be reduced to a greater extent than heretofore.

A damping water required amount m required for correction speed vEin is obtained concerning correction plates 47, 53 the design areal ratios of which are known and are minimum and maximum respectively and are made to be interpolation points 59, 61. The design areal ratio between the maximum design areal ratio and the minimum design areal ratio of the correction plates 47, 53 of the plate to be used for the next printing job is obtained. The damping water amount required for the next printing job which users the plate which is scheduled for the next printing job at the correction speed vEin is obtained by interpolating the damping water between the interpolation points 59, 61. The characteristic curbed line 65 of the damping water required amount which is required for the next printing job and corresponds to the printing speed v is obtained and the damping water supply, while the printing job is executed, is controlled along the characteristic curved line 65.