To always sufficiently condense laser beam by mounting a laser irradiation device irradiating the plate attached to a plate cylinder capable of being rotationally driven with laser beam so as to be capable of moving the same in two directions, that is, the longitudinal axial direction of the plate cylinder and the laser beam irradiation direction crossing the longitudinal axial direction at a right angle.

A laser irradiation device 11 is provided so as to be movable in two directions, that is, the longitudinal axial direction of a plate cylinder 1 and the laser beam irradiation direction crossing the longitudinal axial direction at a right angle. That is, both shaft parts of the plate cylinder 1 being a roll body are supported by bearings and a drive means is connected to one shaft part to make the plate cylinder 1 rotatable in the direction shown by an arrow at a constant speed. A plate 2 made of a resin is attached to the outer peripheral surface of the plate cylinder 1 in a detachable manner by a proper fixing means, for example, a bolt. The laser irradiation device 11 consists of the Y-table 3 movable in the longitudinal axial direction of the plate cylinder 1 and the X-table 4 movable in the laser beam irradiation direction crossing the longitudinal axial direction at a right angle and a lens 7, a laser output part 8 or the like are provided on the X-table 4.