PURPOSE: To improve the efficiency of printing work for a sheet by arranging two ink transferring devices or more on a printing cylinder provided in the process of feeding sheet to be switchable alternately between the transferring position and the rest position.

CONSTITUTION: In a printing machine for corrugated board sheets and the like, two ink transferring devices or more 6 are provided on a printing cylinder 2 set up in the process of feeding sheets. A swithcing mechanism comprising a turning control shaft 13, a rack 17, a rod 16, an air cylinder 15 and the like is provided below ink transferring devices made up of an ink roller 7 and a transferring roller 9. The switching mechanism tilts the transferring roller 9 with a drive shaft 8 of the ink roller 7 as the fulcrum so that it can be switched from the transferring position of contacting a printing plate 3 rotatively to the rest position of separating therefrom. This alternately switches several ink transferring devices 6 between the transferring position and the rest position thereby enabling quick change of the printing color.