  We study transport through a quantum dot coupled to normal and
superconducting leads using the numerical renormalization group method. We show
that the low-energy properties of the system are described by the local Fermi
liquid theory despite of the superconducting correlations penetrated into the
dot due to a proximity effect. We calculate the linear conductance due to the
Andreev reflection in the presence of the Coulomb interaction. It is
demonstrated that the maximum structure appearing in the conductance clearly
characterizes a crossover between two distinct spin-singlet ground states, i.e.
the superconducting singlet state and the Kondo singlet state. It is further
elucidated that the gate-voltage dependence of the conductance shows different
behavior in the superconducting singlet region from that in the Kondo singlet
region.
