A fan structure includes an upper cover, a fan frame body, a bearing cup, a bearing, a stator assembly, a hub and a shaft rod. The upper cover is mated with the fan frame body to together define a receiving space in which the bearing cup is disposed. The bearing cup has an open end and a closed end. The bearing is disposed in the bearing cup. The stator assembly is fitted around the bearing cup. The hub has multiple outward extending blades spaced from the upper cover by a first distance. The shaft rod has a connection end connected with the hub and a protruding end passing through the shaft hole and protruding from the bearing to abut against the closed end of the bearing cup and define a second distance. The first distance is smaller than the second distance to avoid deflection of the shaft rod.