To provide a pierced nut surely preventive of idle run during tightening while maintaining a tightening bearing surface of the pierced nut for preventing the depression of a metal plate.

The pierced nut 1 comprises an inner cylinder portion 3 having a screw hole 2, suspended at the center of the lower face of a nut body, an outer cylinder portion 4 provided at the peripheral edge of the lower face of the nut body 10, an annular groove 5 formed between the inner cylinder portion 3 and the outer cylinder portion 4, and a groove 7 radially provided in the lower face of the outer cylinder portion 4. A protruded locking portion 6 is provided at the opening end of a side wall of the groove 7 so that the pierced nut 1 can be fixed to the metal plate 8 by biting the metal plate 8 into the groove 7 for engaging the locking portion 6.