A piercing nut according to the present invention includes an internal thread 11, a ring-shaped punching part 12, a ring-shaped groove 16, and a bearing surface 17. The internal thread 11 is formed at the center of a nut main body 10. The ring-shaped punching part 12 protrudes around the outer periphery of the internal thread 11. The ring-shaped groove 16 is formed around the outer periphery of the ring-shaped punching part 12. The bearing surface 17 protrudes around the outer periphery of the ring-shaped groove 16. The height h of the ring-shaped punching part 12 is equal to or lower than the height H of the bearing surface 17 in the opposite manner to the conventional technique.