  The axial-vector coupling constant in nuclear medium is systematically
studied using chiral perturbation theory. For normal nuclear matter, the first
non-trivial corrections are estimated based on the independent particle
approximation taking into account nuclear correlations in nuclear medium. The
one-pion-exchange (OPE) two-body interactions turn out to enhance the coupling
constant by $\delta g_A/g_A\simeq (0.09 \sim 0.15)$. The role of the
four-nucleon contact interaction, whose low-energy constants are yet to be
determined, is analyzed in connection with the empirical quenching factor of
$\delta g_A/g_A\simeq -0.2$ in the presence of the nuclear short-range
correlation. Conventional approaches are discussed in the light of our result.
