  We report on the accuracy of the measurement of the two photon decay width of
a Higgs boson with the mass of 120 GeV at the TESLA Photon Collider, assuming a
$\gamma \gamma$ integrated luminosity of 80 fb$^{-1}$ in the hard part of the
spectrum. The QCD radiative corrections for the quark pair background processes
are taken into account by a reweighting procedure. We found that the product
$\Gamma (\rm H \to \gamma \gamma) \times \rm BR (\rm H \to \rm b \bar{\rm b})$
can be measured with the statistical error of 1.8% in one year of run.
