  We report on new attempt to investigate baryon-baryon interactions in lattice
QCD. From the Bethe-Salpeter (BS) wave function, we have successfully extracted
the nucleon-nucleon ($NN$) potentials in quenched QCD simulations, which
reproduce qualitative features of modern $NN$ potentials. The method has been
extended to obtain the tensor potential as well as the central potential and
also applied to the hyperon-nucleon ($YN$) interactions, in both quenched and
full QCD.
