A plate attachment device to be fixed to a plate drive shaft of a printing machine for attaching a printing plate including a cylindrical plate main body and a printing portion formed on a part of an outer peripheral portion of the cylindrical plate main body, comprising: a plate cylinder configured to be fixedly mounted on an outer periphery of the plate drive shaft and having a cylindrical plate attaching surface to which the printing plate is to be attached from a tip end side of the print drive shaft, characterized in that the plate attachment device further comprises: a plurality of plate securing members (121, 171) arranged at the plate attaching surface so as to be movable in both radially outward and inward directions of the plate cylinder and configured to come into contact with the printing plate attached to the plate attaching surface to increase a diameter of the printing plate to closely attach the printing plate to the plate attaching surface, wherein at least a part of the plurality of plate securing members (121, 171) includes a contact surface which comes into contact with an inner peripheral portion of the printing plate, the contact surface being formed to have a curved shape having a same curvature as an outer peripheral surface of the plate cylinder, wherein the contact surface is configured to be positioned at a same height as the plate attaching surface of the plate cylinder when the printing plate is in close contact with the plate attaching surface. a plate cylinder configured to be fixedly mounted on an outer periphery of the plate drive shaft and having a cylindrical plate attaching surface to which the printing plate is to be attached from a tip end side of the print drive shaft, characterized in that the plate attachment device further comprises: a plurality of plate securing members (121, 171) arranged at the plate attaching surface so as to be movable in both radially outward and inward directions of the plate cylinder and configured to come into contact with the printing plate attached to the plate attaching surface to increase a diameter of the printing plate to closely attach the printing plate to the plate attaching surface, wherein at least a part of the plurality of plate securing members (121, 171) includes a contact surface which comes into contact with an inner peripheral portion of the printing plate, the contact surface being formed to have a curved shape having a same curvature as an outer peripheral surface of the plate cylinder, a plurality of plate securing members (121, 171) arranged at the plate attaching surface so as to be movable in both radially outward and inward directions of the plate cylinder and configured to come into contact with the printing plate attached to the plate attaching surface to increase a diameter of the printing plate to closely attach the printing plate to the plate attaching surface, wherein at least a part of the plurality of plate securing members (121, 171) includes a contact surface which comes into contact with an inner peripheral portion of the printing plate, the contact surface being formed to have a curved shape having a same curvature as an outer peripheral surface of the plate cylinder, wherein the contact surface is configured to be positioned at a same height as the plate attaching surface of the plate cylinder when the printing plate is in close contact with the plate attaching surface.