To achieve a good balance among the magnetic field intensity, region of
homogeneous magnetic field intensity and cost, a magnetic field
generating apparatus for generating a magnetic field in a vertical
direction comprises: a pair of magnets having respective magnetic poles
with mutually opposite polarities disposed to face each other in a
vertical direction, for generating a static magnetic field having
different dimensions of its region of homogeneous magnetic field
intensity in two mutually orthogonal directions in a horizontal plane; a
pair of planar magnetic elements, each element supporting respective one
of the pair of the magnets; and a vertical columnar magnetic element
lying in a direction different from the two directions, each end of which
is joined to respective one of the pair of the planar magnetic elements.