A stator core includes an end portion, a first pole arm, and a second pole arm. The first pole arm includes two first connecting arms extending from the end portion and spaced from each other, and two first pole claws respectively formed at ends of the first connecting arms. The first pole claws are spaced from each other with an opening formed there between. The second pole arm includes two second connecting arms axially stacked to the two first connecting arms respectively and two second pole claws respectively formed at distal ends of the two second connecting arms. The two second connecting arms are connected with each other.