To provide a bolt having the nut fall preventive function which can reduce the execution labor, simplify the work, and reliably prevent any fall of a nut.

This bolt has a bolt shaft 3 with a male screw 4 formed thereon and a fall preventive member 5 to lock the nut 6. The fall preventive member 5 integrally comprises a base part 50 extended straight from the center of the shaft at a tip of the bolt shaft 3 to a tip side, an elastic deformation part 52 curved in a C-shape, and a straight locking part 53 with a space from the base part 50 expanding inwardly in the axial direction of the bolt shaft 3. The locking part 53 is located inside a storage part 32 cut in the axial direction in a forming part of the male screw 4, a tip 53a of a locking part is protruded from the male screw 4, and the locking part 53 can be retracted in the storage part 32 by the elastic deformation of the elastic deformation part 52.