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 Δ m_12^2, sin^22θ_12, Δ m_23^2, θ_13 and θ_23. The mass parameter Δ m^2_23 is restricted to

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... 1eV^2-0.0002eV^2. For mixing parameters, there is no difference between the large θ_12 angle solution and the small one, and θ_13<13degrees, 28degrees<θ_23<37degrees and 53degrees< θ_23<62degrees for Δ m_23^2=0.01eV^2, θ_13<23degrees and 29degrees<θ_23<61degrees for Δ m_23^2=0.00eV^2, 4degrees< θ_13<22degrees and 38degrees<θ_23<54degrees for Δ m_23^2 =0.0002eV^2.