  We investigate resonant spin-flavor (RSF) conversions of supernova neutrinos
which are induced by the interaction of neutrino magnetic moment and supernova
magnetic fields. From the formulation which includes all three-flavor neutrinos
and anti-neutrinos, we give a new crossing diagram that includes not only
ordinary MSW resonance but also magnetically-induced RSF effect. With the
diagram, it is found that four conversions occur in supernova, two are induced
by the RSF effect and two by the pure MSW. We also numerically calculate
neutrino conversions in supernova matter, using neutrino mixing parameters
inferred from recent experimental results and a realistic supernova progenitor
model. The results indicate that until 0.5 seconds after core bounce, the
  RSF-induced $\bar{\nu}_e \leftrightarrow \nu_\tau$ transition occurs
efficiently (adiabatic resonance), when $\mu_\nu \agt 10^{-12} \mu_B
  (B_0 / 5 \times 10^{9} \mathrm G)^{-1}$, where $B_0$ is the strength of the
magnetic field at the surface of iron core. We also evaluate the energy
spectrum as a function of $\mu_\nu B_0$ at the SuperKamiokande detector and the
Sudbury Neutrino Observatory using the calculated conversion probabilities, and
find that the spectral deformation might have possibility to provide useful
information on neutrino magnetic moment as well as magnetic field strength in
supernovae.
