[Object] To prevent a tip body from being greatly cut out by a fitting hole to secure strength of a tip without complicating the shape of a head portion of a clamp member or a fitting hole of a tip body.
[Solving Means] There is provided a clamp mechanism of a tip for pressing the tip, in which a fitting hole 5 is formed through a tip body 1, by the use of a clamp member 13 having a shaft portion inserted into the fitting hole 5 and a head portion 13B with an outer diameter larger than that of the shaft portion and thus clamping the tip to a tip fitting seat 12. In the clamp member 13, a section, which is perpendicular to the central axis line O, of the back surface 13C of the head portion 13B has a circle shape centered at the central axis line O. In the tip body 1 of the tip, the head portion 13B of the clamp member 13 can pass through the fitting hole 5, and a contact portion 5B with which a part of the back surface 13C of the head portion 13B comes in contact at the time of advancing the clamp member 13 is formed in an opening of the fitting hole 5.