  Radiatively-induced neutrino mass matrix is investigated within the framework
of an SU(5) SUSY GUT model. The model has matter fields of three families
\bar{5}_{L(+)i}+5_{L(+)i} in addition to the ordinary matter fields
\bar{5}_{L(-)i}+10_{L(+)i} and Higgs fields H_{(+)}+\bar{H}_{(0)}, where
(+,0,-) denote the transformation properties (\omega^{+1},\omega^0,\omega^{-1})
(\omega^3=+1) under a discrete symmetry Z_3. R-parity violating terms are given
by \bar{5}_{L(+)} \bar{5}_{L(+)} 10_{L(+)}, while the Yukawa interactions are
given by \bar{H}_{(0)} \bar{5}_{L(-)} 10_{L(+)}, i.e. the \bar{5}-fields in
both are different from each other. The Z_3 symmetry is only broken by the
terms \bar{5}_{L(+)i}5_{L(+)i} softly, so that the
\bar{5}_{L(+)i}\leftrightarrow \bar{5}_{L(-)i} mixings appear at \mu < M_X. Of
the R-parity violating terms \bar{5}_{L(+)} \bar{5}_{L(+)} 10_{L(+)}, only the
terms (e_L\nu_-\nu_Le_)e_R^c sizably appear at \mu < M_X.
