  The electroweak phase transition and the sphaleron decoupling condition in
the MSSM are revisited taking the latest experimental data into account. The
light Higgs boson scenario and the ordinary decoupling limit which are
classified by the relative size between the CP-odd Higgs boson mass and Z boson
mass are considered within the context of electroweak baryogenesis. We
investigate v/T at not only the critical temperature at which the effective
potential has two degenerate minima but also the nucleation temperature of the
critical bubbles, where v is a vacuum expectation value of the Higgs boson and
T denotes a temperature. It is found that v/T at the nucleation temperature can
be enhanced by about 10% compared to that at the critical temperature. We also
evaluate the sphaleron decoupling condition including the zero mode factors of
the fluctuations around sphaleron. It is observed that the sphaleron decoupling
condition at the nucleation temperature is given by v/T>1.38 for the typical
parameter sets. In any phenomenologically allowed region, v/T at both the
critical and nucleation temperatures cannot be large enough to satisfy such a
sphaleron decoupling condition.
