To make continuous cutting with simultaneous removal of burrs in the forefront part left unremoved in the first working process without requiring the operator to shift his working position forward and backward relative to a metal plate or to revolve the metal plate by changing the grasp of a chamfering cutter to the opposite side.

A cutter part 2 is installed at the forefront of a shank 1 equipped at the base end with a gripping part 1a and is furnished with an overhang part 21 hanging over to the left and right and an extension part 20 in the central part as stretching downward, and cutting edges 23 continued in hooked shape in the rear view are formed on the left and right side edges of the extension part 20 and the left and right bottom edges of the overhang part 21, and a platform 25 for placing is formed on the undersurface of the extension part 20.