An inking unit for use in a rotary printing machine is disclosed. A plurality of endless belts are placed side by side along the surface of a driving roller. These belts transport a liquid medium such as printing ink or damping fluid along the surface of a covering of a cylinder in the direction of the longitudinal axis of the cylinder. The liquid medium is transported by the belts from a position of excess ink to a position of less ink thereby ensuring a uniform distribution of the liquid along the surface of the roller.