  Recent progress of lattice QCD study of nuclear forces (potentials) is
reviewed. Scattering phase shift is an important observable for two particle
system. In lattice QCD, phase shifts are calculated from long distance behavior
of Bethe-Salpeter (BS) wave functions by Luescher's finite volume method. For
applications to nuclear physics of multi-nucleon system, it is more
advantageous to convert the information of phase shifts in the form of
potentials. We therefore extend the method so as to generate the potentials
from BS wave functions. These potentials are faithful to scattering phase shift
by construction, because they can reproduce BS wave functions in which the
information of phase shift is embeded in the long distance part.The method was
first applied to the central potential in NN system. It is now applied to many
objects, such as tensor potential, hyperon potentials, energy dependence of
nuclear potentials, and investigations of the repulsive core at short distance.
