In a motor comprising a stator assembly and a rotor assembly housed inside the stator assembly, a bobbin is structured to be oval-cylindrical in its radial cross section, rather than circular-cylindrical, such that a body section of the bobbin is composed of four continuous walls, two of which are formed of flat plates oriented perpendicular to the minor axis of the oval and disposed opposite to each other in parallel, and the other two of which are formed of outwardly arced plates oriented perpendicular to the flat walls and disposed opposite to each other in a symmetric manner. Pole teeth are provided only at portions corresponding to the arced walls to thereby reduce the dimension between the flat walls for downsizing while allowing an increased number of turns of a magnet wire wound around the bobbin.