<p>This embodiment of a magnetic separation device has: a plurality of magnetic separation columns of which a plurality are disposed in series and that have a plurality of filters comprising a non-magnetic cylinder of which the hollow center is the flow path for water to be processed, and a magnetic body disposed in a manner so as to be perpendicular to the flow of water to be processed within the cylinder; and a magnetic field imposition device that imposes a magnetic field to a portion of the magnetic separation columns, has a size that corresponds to the portion of magnetic separation columns, and is provided slidably to the outside of the plurality of magnetic separation columns.</p>
