To solve the problem wherein a raised temperature of a threading tool causes deformation thereof in a short period and resultantly a flaw such as a crack in a thread groove.

A threading tool 1 is so constructed that the periphery of a columnar body 2 is provided with a plurality of annular projections 3 with a circular periphery at given pitches P, and that the surfaces of the annular projections 3 are coated with a hard film 4 of a Knoop hardness of 40 GPa or more. Each annular projection 3 has grooves 5 notched in an axial direction of the columnar body 2. In the plan view of the annular projections 3, those pointed corners of each annular projection 3 which are contiguous to the grooves 5 have an obtuse angle.