A highly stable and durable fan bearing structure practical for small electronic device application is disclosed to include a bearing block, which has a stepped hub defining a vertically extending axle hole and an inside annular flange inside the axle hole at a distance away from the top opening of the axle hole, a fan blade assembly, which has permanent magnets mounted in a hollow base block thereof and an axle suspending in the hollow base block and inserted into the axle hole and coupled to the inside annular flange of the stepped hub and kept in coincidence with the central axis of the axle hole, and a stator module accommodated in the hollow base block of the fan blade assembly for acting against the permanent magnets to cause rotation of the fan blade assembly upon connection of an electric current.