  We investigate the pion electromagnetic charge radii and mass dropping of the
rho meson at finite density. We first calculate the pion charge radii within
the framework of the nonlocal chiral quark model from the instanton vacuum both
at zero and finite densities. In order to relate the change of the pion charge
radius to that of the rho-meson mass at finite density, we employ the
vector-meson dominance for the pion electromagnetic form factor. It turns out
that the pion charge radius is getting larger as the quark chemical potential
increases. As a result, the rho-meson mass falls off as the quark chemical
potential grows and is found to be dropped by about 10% at normal nuclear
matter density: m*_rho/m_rho ~ 1 - 0.12 mu_B/mu_0, which is compatible to the
results of the measurement at the KEK recently.
