To provide a tool for chamfering an end face of a tube, configured to form a groove or the like on the end face of a metallic tube having a comparatively small diameter quickly and easily, with a simple structure.

The tool 1 for chamfering an end face of a tube includes an insertion part 2, a chip mounting part 5, and a base shaft part 3 along an axis C direction. The insertion part 2 is a columnar body to be inserted to the inside 25 of the tube P from an opening at the end of the tube. The chip mounting part 5 has: a columnar part 6 having a diameter larger than the diameters of the insertion part 2 and base shaft part 3 adjacent thereto; a fixed surface 7 which is formed in a triangular shape along the radial direction from the outer circumferential side of the columnar part 6, is made parallel to the center axis C, and includes the center axis C; and a chip fixing part ch including a pair of longitudinal side faces 9a, 9b, holding the fixed surface 7 and inclined symmetrically along the radial direction. A female screw hole 8 for receiving a fixing screw 17 passing through the center of a triangular cutting chip 20, is opened on the fixed surface 7.