To improve a platemaking accuracy and a printing accuracy and to improve a productivity.

The platemaking unit 35 is movable between an operating position capable of platemaking and a non-operating position capable of replacing the plate in a direction of arrows A-B. A first engaging block 48A having an engaging groove 49 of a V shape as seen from a side face and a second engaging pin 50 are provided in the unit 35. Meanwhile, a first engaging pin 29A and a second engaging block 31 having an engaging recess 32 of a V shape as seen from a plane are provided in the frame. The operating position of the unit 35 is positioned by engaging the first block 48A with the first pin 29A or the second pin 50 with the second block 31.