The invention relates to an outer circle chamfering tool. The outer circle chamfering tool comprises a cutter bit of which the rotation axis extends in the up-and-down direction, and the cutter bit isof an integral structure and at least two cutting portions distributed at intervals in the circumferential direction are arranged at the lower end of the cutter bit. Flank tool faces are arranged onthe inner sides of the cutting portions, and the flank tool faces are arranged towards the outer side of the cutter bit in an inclined mode from top to bottom to form a flaring structure at the lowerend of the cutter bit. The intersection lines between rake tool faces and the flank tool faces of the cutting portions form chamfering cutting edges inclined towards the outside of the cutter bit fromtop to bottom. According to the outer circle chamfering tool, when a workpiece to be machined is chamfered for the outer circle, a part to be machined protrudes into the flaring structure of the cutter bit, and the inclined chamfering cutting edges chamfer the outer circle of the part, so that the cutter bit can be applied to the parts to be machined of different diameters to increase the application range of the tool.