Magnetic fluid sealing device and magnetic fluid sealed bearing

A magnetic fluid sealed bearing, comprising:

• an inner ring and an outer ring, both formed of a magnetic material;
• a plurality of rolling elements interposed between the inner ring and the outer ring;
• a ring-shaped polar plate disposed on an opening side between the inner ring and the outer ring, the polar plate having a magnet mounted thereto;
• and
• a magnetic fluid retained in a gap between the polar plate and the inner ring or in a gap between the polar plate and the outer ring, so as to seal the plurality of rolling elements,
• wherein the polar plate has a non-magnetic spill preventing portion provided thereon, the spill preventing portion having a projecting wall that is disposed distant from an end surface of the polar plate retaining the magnetic fluid, so as to prevent spill of the magnetic fluid