To add coming-off prevention and turning prevention functions to an insert fitting by contriving a shape of grooves formed on an outer peripheral surface of a cylindrical shaft body.

The insert fitting is provided with a collar 12 on one end of the cylindrical shaft body 11. A small-diameter cylindrical shaft part 14 is formed on the other end of the cylindrical shaft body 11 through a tapered part 13. A plurality of inclined engaging grooves 15, 16 and the like are formed from the tapered part 13 along the cylindrical shaft body 11 so that the engaging grooves 15, 16 and the like incline with respect to an axial direction of the cylindrical shaft body 11, and that the inclination directions of the adjacent inclined engaging grooves 15 and 16 with respect to the axial direction are opposite to each other.