Abstract: A cutting device for plate materials relatively transfers a plate material and cutter blades and cuts the plate material with a cutting portion of the cutter blades. The cutting portion is provided with a plurality of projecting cutter blades. The plurality of projecting cutter blades are separately disposed at fixed intervals in the direction which the plate material is transferred to the cutter blades and gradually projected larger toward the direction in which the plate material advances. The plurality of projecting cutter blades have inclined cutting edges which are acute cutting edges for cutting the plate material in such a manner as to be gradually inserted deeper into the plate material transferred to the cutter blades. The inclined cutting edges are inclined toward the direction in which the plate material is transferred so as to be gradually inserted deeper into the plate material.