  We discuss the measurement of new physics in long baseline neutrino
oscillation experiments. Through the neutrino oscillation, the probability to
detect the new physics effects such as flavor violation is enhanced by the
interference with the weak interaction. We carefully explain the situations
that the interference can take place. Assuming a neutrino factory and an
upgraded conventional beam, we estimate the feasibility to observe new physics
numerically and point out that we can search new interactions using some
channels, for example $\nu_{\mu} \to \nu_{\mu}$, in these experiments. We also
discuss several models which induce the effective interactions interfering with
the weak interaction, and show that some new physics effects are large enough
to be observed in the oscillation enhanced way.
