To suppress lowering of printing quality and also stabilize printing quality.

A printing unit 1 is equipped with a printing roller group comprising a plate cylinder 27 whereon a printing plate is mounted and a blanket cylinder 28, and with an ink roller group which supplies the printing plate mounted on the plate cylinder 27 with ink supplied from an ink supply source. The printing roller group and the ink roller group are driven by driving force taken out from an impression cylinder 29. On the occasion, the driving force that drives the ink roller group is transmitted to the ink roller group through the intermediary of an ink supply arrangement driving mechanism 50.