PURPOSE: To perform chamfering efficiently and provide a fine machined surface.

CONSTITUTION: A chamfering device is provided with a cutter 12 for cutting the corner of a plate 1, a cutter supporting base 20 for supporting the cutter 12 movably in a fixed direction, a workpiece supporting bed 50 for supporting the plate 1 in the state of the plate 1 being inclined by 40° to the moving direction of the cutter 12, and a workpiece keep 30 for pressing the plate 1 to the workpiece supporting bed 50. A sliding contact face 14 parallel to the moving direction of the cutter 12 is formed at the cutter 12, on the opposite side to the plate 1, and a cutting edge escape regulating face 24 coming in contact with the sliding contact face 14 of the cutter 12 is formed at the cutter supporting bed 20.