An electromagnetic driving unit includes a rotor having a central shaft and formed
of a permanent magnet with a hollow cylindrical shape; an inner yoke disposed on
an inner circumferential side of the rotor; an outer yoke disposed on an outer
circumferential side of the rotor; and a coil for exciting the inner yoke and outer
yoke. The inner yoke has a shaft portion at an end portion thereof inserted into
the rotor, and the shaft portion has a circular cross-section or an oval cross-section
perpendicular to an axial direction of the shaft portion. The rotor has a bearing
recess in an inner circumferential wall thereof, so that the shaft portion of the
inner yoke slidably fits in the bearing recess.
