  The existence of an anomalous U(1) symmetry is shown to play a crucial role
in the supersymmetric radiative seesaw model for neutrino masses. It explains
the smallness of some couplings related to neutrino mass generation in a
favorable way in addition to cause the hierarchical structure of Yukawa
couplings of quarks and leptons. If it is spontaneously broken to a $Z_2$
subgroup, this $Z_2$ symmetry can make a lifetime of the lightest field with
its odd parity extremely long. Thus, the model has an additional dark matter
candidate other than the lightest neutralino, which appears in the $R$-parity
conserved MSSM. We discuss the nature of dark matter by taking account of its
relation to the neutrino mass generation and the lepton flavor violation.
