The invention discloses an outer clamp type bevelling machine, which comprises a power mechanism, a driving transmission gear, left and right movable rings, left and right gear rings and left and right fixed rings, wherein the left and right movable rings are respectively and fixedly arranged on the left and right gear rings, a plurality of eccentric shafts are respectively and fixedly arranged on the left and right fixed rings in the circumferential direction, each eccentric shaft comprises a shaft body and a cylindrical bulge part arranged at one end of the shaft body, the axial line of each shaft body and the axial line of the corresponding cylindrical bulge part are parallel but do not coincide, the shaft body of each eccentric shaft is fixedly arranged on the left and right fixed rings, a rolling wheel bearing is arranged on each cylindrical bulge part, a plurality of rolling wheel bearings are movably embedded in grooves of the inner side surfaces of the left and right gear rings, the driving transmission gear is engaged with the left and right gear rings, the power mechanism drives the driving transmission gear to rotate, a knife rest holder is fixedly arranged on the front end surface of the left movable ring or the right movable ring, and the front end surface of the left movable ring or the right movable ring is fixedly provided with a knife impacting mechanism. The outer clamp type bevelling machine has the advantages that the relative rotation can be realized, good coaxiality is also realized, during the cutting, the operation stability is high, the stable and smooth rotation can be realized, the cutting precision is high, and the risk of gear clamping and gear stubbing is also greatly reduced.