To provide a torque nut, eliminating waste in materials and being capable of surely fastening.

This torque nut is provided with first and second hexagon nut parts 2 and 3 formed with female hexagonal screw parts 5 and 5a in their inside, and a thin-wall portion 4, having its inside diameter larger than the diameter of troughs of the female screw parts 5 and 5a, integrally connecting the first and the second hexagon nut parts 2 and 3 thereto, and sheared by a prescribed torque applied to the second hexagon nut part 3 disposed on the outside. The width of the inner circumferential part 4a of the thin-wall part 4 is formed twice as large as the pitch of the female screw parts 5 and 5a or more, and the two-plane width of the second hexagonal nut part 3 is formed larger than the diagonal distance of the first hexagonal nut part 2 or the two- plane width of the second hexagonal nut part 3 is formed smaller than the two-plane width of the first hexagonal nut part 2.