  We analyze the atmospheric neutrino experiments of SuperKamiokande (535 days)
using the three-flavor neutrino framework with the mass hierarchy m_1 nearly
equal m_2 << m_3. We study the event ratios of sub-GeV, multi-GeV and upward
through-going muons zenith angle distributions. Taking into account the
atmospheric and terrestrial experiments, we obtain the allowed regions of mass
and mixing parameters \Delta m_{12}^2, sin^22\theta_{12}, \Delta m_{23}^2,
\theta_{13} and \theta_{23}. The mass parameter \Delta m^2_{23} is restricted
to 0.01eV^2-0.0002eV^2. For mixing parameters, there is no difference between
the large \theta_{12} angle solution and the small one, and
\theta_{13}<13degrees, 28degrees<\theta_{23}<37degrees and 53degrees<
\theta_{23}<62degrees for \Delta m_{23}^2=0.01eV^2, \theta_{13}<23degrees and
29degrees<\theta_{23}<61degrees for \Delta m_{23}^2=0.00eV^2, 4degrees<
\theta_{13}<22degrees and 38degrees<\theta_{23}<54degrees for \Delta m_{23}^2
=0.0002eV^2.
