PURPOSE: To allow the replacement of a form cylinder, a blanket cylinder, and an impression cylinder, etc., to be practicable without the need of a disassembly work by permitting gears in the driving side and driven side to be in mesh engagement with each other when the printing cylinder unit is mounted on the printing cylinder unit mounting part of a main machine unit.

CONSTITUTION: In a state where the printing cylinder unit 15 is mounted on the printing cylinder unit mounting part 13 of a main machine unit 11, an intermediate shaft 69 is driven in the axial direction by an air cylinder device 79, and the driven side spur gear 73 is located on the engaging position indicated by real line, thereby engaging the driving side spur gear 73 and driven side spur gear 87. In this way, the rotation of a main driving shaft 9 is transmitted to a driving side bevel gear 59, driven side gear 65, spur gear 67, driving side spur gear 73, and driven side spur gear 87, and further it is thereby transmitted to spiral bevel gears 89, 95, resulting in the rotation driving of an upper form cylinder 47, an upper blanket cylinder 49, a lower form cylinder 51, and a lower blanket cylinder 53.