To provide a chamfering apparatus chamfering plaster board or the like efficiently with less labor.

On an L-shaped base member 16 brought into contact with the surface and the side face of a material to be chamfered such as a plaster board 10 via a lateral part 12 and a vertical part 14, a disc cutter 18 with a tilted blade face for chambering the corner of the material to be chambered positioned at the corner part between the lateral part 12 and the vertical part 14 is mounted rotationally to a mounting shaft arranged in the longitudinal substantial center position of the base member 16.