A waterproof and salt spray-resistant fan motor structure includes a base, a stator assembly, a case, and at least one circuit board. The base has a bearing cup vertically projected from one side thereof. The stator assembly is externally fitted around the bearing cup, and includes a plurality of silicon steel plates having windings mounted thereon. The case is arranged between the base and the stator assembly and internally defines a closed space, and the circuit board is located in the closed space. With these arrangements, the case protects the circuit board against corrosion by water and salt spray, enabling a fan to have largely extended service life.