  In hole-doped high-Tc cuprates, the Nernst coefficient (\nu) as well as the
magnetoresistance (\Delta\rho/\rho) increase drastically below the pseudo-gap
temperature, T^*. This unexpected result attracts much attention in that it
reflects the fundamental feature of the electronic state in the pseudo-gap
region, which has been a central issue on high-Tc cuprates. In this letter, we
study these transport phenomena in terms of the fluctuation-exchange
(FLEX)+T-matrix approximation. In this present theory, the d-wave
superconducting (SC) fluctuations, which are mediated by antiferromagnetic (AF)
correlations, become dominant below T^*. We focus on the role of the vertex
corrections both for the charge current and the heat one, which are
indispensable to keep the conservation laws. As a result, the mysterious
behaviors of \nu and \Delta\rho/\rho, which are the key phenomena in the
pseudo-gap region, are naturally explained as the reflection of the enhancement
of the SC fluctuation, without assuming thermally excited vortices. The present
result suggests that the pseudo-gap region in high-Tc cuprates is well
described in terms of the Fermi liquid with AF and SC fluctuations.
