To prevent the generation of hue inferiority by measuring and operating respective ink distributing roller film thicknesses of a specific state condition, a printing plate pattern area ratio and a regulating key opening degree at every ink correspondence at every ink regulating key corresponding region to set them as the opening degree of the corresponding key of an ink fountain to set ink supply quantity at a point of time of the start of printing.

The ink film thickness Ax of an ink distributing roller 6 before the start of printing is measured at every corresponding region of an ink regulating key 5 by a detection head 1 and a main body 2 and the film thickness Bx of a form roller 8 is measured at every correspondence of the key 5 by stopping the supply of ink according to the nip states of the form roller 8, a plate cylinder 7 and blanket cylinders 11, 12 to race the form roller 8, the plate cylinder 7 and the blanket cylinders 11, 12. A printing plate pattern area ratio Dx is calculated from Ax and Bx by an ink regulating key opening degree calculation apparatus 3 and a key opening degree Ix is operated from the printing plate pattern area ratio Esx of a result value, a key opening degree Isx and Dsx and set as the corresponding key opening degree of the ink fountain by an ink regulating key opening degree setting apparatus 4. Therefore, the generation of hue inferiority at a point of time of the start of printing can be reduced.