Atmospheric Neutrino Oscillation and a Phenomenological Lepton Mass Matrix

We propose simple phenomenological lepton mass matrices which describe the three neutrinos almost degenerate in mass, leading to a very large mixing angle between $\nu_\mu$ and $\nu_\tau$, as consistent with a recent report on atmospheric neutrino oscillation from the Superkamiokande collaboration. Our matrix model also gives $\nu_e-\nu_\mu$ mixing in agreement with the value required for neutrino oscillation to explain the solar neutrino problem.