  As well as known, the black hole evaporation problem is famous problem.
Because the S.W.Hawking found the black holes emit light at the future null
infinity as a thermal radiation \cite{H}, we think that the black holes may be
vanish. However, to prove this problem, we should solve field equation, i.e.
forth order partial differential equations \cite{Ford}\cite{BD}. However, we
can find a method to solve this equation, and we could prove that the black
holes finally vanish. To solve this problem we use dynamical horizons equation
in the Vaidya spacetime.
