  Usually, neutrino oscillation experiments are analyzed within the two-flavor
framework which is governed by 1 mass-squared difference and 1 mixing angle.
But there are 6 parameters,2 mass-squared differences, 3 mixing angles, and 1
CP phase within the three-flavor framework.In this article,we estimate the
effect from the smaller mass-squared difference,the other mixing angles, and
the CP phase, which we call three-flavor effect, for the determination of the
mass-squared difference and the mixing angle from the nu_mu's survival and
transition probability with the two-flavor analysis.It is found that the
mass-squared difference from the two-flavor analysis is slightly shifted from
the larger mass-squared difference by the three-flavor effect.The order of
magnitude of the three-flavor effect for the mass-squared difference is
comparable with that of the expected error for the mass-squared difference of
the two-flavor analysis in the future long base-line neutrino oscillation
experiments.The CP phase dependence of the nu_mu to nu_etransition probability
is also shown.
