To alleviate a load of a registering operation by providing a protrusion on at least either a gripper surface of a gripper plate of a plate locking-up device at an opposite side to a gripper end or a gripper surface of a locking-up device bearer in a direction perpendicular to an axial direction of a plate cylinder, thereby effectively regulating a fan-out.

A bent part 39 formed at an end 7b of a plate 7 is engaged with a protrusion 37 projected on a gripper surface 29a of a gripper plate 29A. Both front and rear surfaces of the end 7b of the plate 7 are effectively locked to gripper surfaces 25a and 29a of a plate locking-up device 25 and the plate 29A and held. As a result, the plate 7 is not slide between the surfaces 25a and 29a of the device 25 and the plate 29A. Accordingly, the end 7b of the plate 7 gripped between the gripper surfaces 25a and 29a of a locking-up device bearer 25A and the plate 29A is restricted to move in a direction of an arrow B. Thus, since a fan out is effectively regulated, a load of a registering operation can be alleviated, thereby improving a printing quality.