  To understand the Abelian dominance and magnetic monopole dominance in
low-energy QCD, we rewrite the non-Abelian Wilson loop into the form which is
written in terms of its Abelian components or the 't Hooft-Polyakov tensor
describing the magnetic monopole. This is peformed by making use of a version
of non-Abelian Stokes theorem. We propose a modified version of the maximal
Abelian (MA) gauge. By adopting the modified MA gauge in QCD, we show that the
off-diagonal gluons and Faddeev-Popov ghosts acquire their masses through the
ghost--anti-ghost condensation due to four ghost interaction coming from the
gauge-fixing term of the modified MA gauge. The asymptotic freedom of the
original non-Abelian gauge theory is preserved in this derivation.
