There is provided an insert nut, having an outer hollow portion made of a resin material and an inner hollow portion made of a metal material. The outer hollow portion has a projection functioning as a male screw or wedge formed on an outer surface thereof. The inner hollow portion has a female screw formed on an inner surface thereof. The inner hollow portion is press-fitted to the outer hollow portion by inserting one end of the inner hollow portion into the outer hollow portion to reach a final position. Further insertion of the inner hollow portion is prevented beyond the final position. Said one end of the inner hollow portion is caulked with the outer hollow portion.