  The Schwinger-Dyson equation for the quark in the rainbow approximation at
finite temperature (T) is solved numerically without introducing any ansatz for
the dressed quark propagator. The dymanical quark mass-function and the
wave-function renormalization are found to have non-trivial dependence on
three-momentum, Matsubara-frequency and temperature. The critical temperature
of the chiral phase transition (T_c) and the T-dependence of the quark
condensate are highly affected by the wave-function renormalization. We found
that T_c \simeq 155 MeV which is consistent with the result of the finite
temperature lattice QCD simulation. It is also found that the system is not a
gas of free quarks but a highly interacting system of quarks and gluons even in
the chirally symmetric phase.
