To provide an engagement structure for easily, reliably and precisely engaging bone fixers, which are inserted to transverse holes arranged in a nail main body, with the nail main body.

The intramedullary nail 100 comprises: the nail main body 110 having the transverse holes 114, 115 crossing an axial line; the bone fixers 10, 20 to be inserted to the transverse holes 114, 115; and engagement means 121, 122, 123 facing the transverse holes so as to be engaged with the bone fixers. The engagement means include: a first operation member 121 to be screwed onto the nail main body so as to be movable in an axial direction; a second operation member 122 which is moved to the side of the transverse holes together with the first operation member in a rotatable state with respect to the first operation member; an engagement member 123 which is arranged at the transverse hole side of the second operation member and screwed onto the second operation member so as to be movable in the axial direction; and, moreover, a limit position regulation means 103d for regulating the limit position of the transverse hole side in the axial direction in the first operation member.