  We propose a new mechanism for the prompt emission of gamma-ray burst. In our
model electrons are continuously accelerated in the post shock region via
plasma turbulence. Using the Monte Carlo technique, we mimic the second-order
Fermi acceleration due to plasma turbulence and obtain photon spectra. Since
the acceleration balances with the synchrotron cooling, the observed low-energy
spectral index is naturally explained. The resultant spectra can be consistent
with observed spectra at least below $\sim 1$ MeV. The model also predicts
delayed GeV-TeV emission due to inverse Compton and broad pulse profile of
optical emission in some cases. Although nontrivial assumptions are required to
reproduce MeV-GeV power-law spectra, the model implies the possibility to
explain various kinds of luminosity correlations.
