  We study the topological feature in the QCD vacuum based on the hypothesis of
abelian dominance. The topological charge $Q_{\rm SU(2)}$ can be explicitly
represented in terms of the monopole current in the abelian dominated system.
To appreciate its justification, we directly measure the corresponding
topological charge $Q_{\rm Mono}$, which is reconstructed only from the
monopole current and the abelian component of gauge fields, by using the Monte
Carlo simulation on SU(2) lattice. We find that there exists a one-to-one
correspondence between $Q_{\rm SU(2)}$ and $Q_{\rm Mono}$ in the maximally
abelian gauge. Furthermore, $Q_{\rm Mono}$ is classified by approximately
discrete values.
