Abstract
A lot of information on the mixing matrix and the mass squared differences of neutrino oscillation have been revealed recently thanks to various experiments on neutrino oscillation. The conclusion is that almost everything is well accounted for by neutrino oscillation among three flavors. In this article I will describe how the three flavor mixing matrix is derived and the status of four neutrino mixing scenarios which would be necessary to account for the LSND experiment in Los Alamos and I will explain on phenomenology of long baseline experiments (determination of the third mixing angle, the mass squared difference of the atmospheric neutrino oscillation and the CP violating phase in the three flavor framework) which are studied actively at present.
