Abstract: A chamfering apparatus for chamfering a work has an adapter which surrounds a tool support, has one end fixed to a casing and the other end projecting from the casing, and is arranged coaxially with the axis of a rotating shaft. This chamfering apparatus includes an eccentric ring rotatably mounted around the adapter, a lock plate rotatably mounted around the eccentric ring, a work guide attached to the lock plate and having a predetermined guide direction to guide a tool support along the work, and keeping means for keeping the angle between the guide direction of the work guide and the output shaft of a motor at a predetermined value when the lock plate and the work guide are translated with respect to the axis of the rotating shaft by rotating the eccentric ring with respect to the adapter.