An electric motor has a rotor, a stator and brushes. The rotor has a shaft, a rotor core fixed to the shaft and having a plurality of teeth, a commutator fixed to the shaft adjacent the rotor core and having a plurality of segments, and rotor winding units wound about the teeth and connected to the commutator segments. Each of the rotor winding units is connected to a pair of adjacent commutator segments. At least one of the rotor winding units has at least two coils connected in series. Each coil has at least two subcoils directly connected in series and separated from each other by at least one tooth. An initial subcoil and a final subcoil of each coil are respectively connected to a pair of segments.