  Vertical magnetic fields have been known to exist in the internetwork region
for decades, while the properties of horizontal magnetic fields have recently
been extensively investigated with \textit{Hinode}. Vertical and horizontal
magnetic fields in the internetwork region are considered to be separate
entities and have thus far not been investigated in a unified way. We discover
clear positional association between the vertical and horizontal magnetic
fields in the internetwork region with \textit{Hinode}. Essentially all of the
horizontal magnetic patches are associated with the vertical magnetic patches.
Alternatively, half of the vertical magnetic patches accommodate the horizontal
magnetic patches. These horizontal patches are located around the borders of
the vertical patches. The intrinsic magnetic field strength as obtained with
the Stokes $V$ line ratio inside the horizontal patches is weak, and is in
sub-equipartition field regime ($B<700$ G), while the field strength outside
the horizontal patches ranges from weak to strong (kG) fields. Vertical
magnetic patches are known to be concentrated on mesogranular and supergranular
boundaries, while the horizontal magnetic patches are found only on the
mesogranular boundaries. These observations provide us with new information on
the origin of the vertical and horizontal internetwork magnetic fields, in a
unified way. We conjecture that internetwork magnetic fields are provided by
emergence of small-scale flux tubes with bipolar footpoints, and the vertical
magnetic fields of the footpoints are intensified to kG fields due to
convective collapse. Resultant strong vertical fields are advected by the
supergranular flow, and eventually form the network fields.
