  In the framework of the perturbative QCD we investigate heavy particle mass
effects on the unpolarized and polarized photon structure functions,
$F_2^\gamma$ and $g_1^\gamma$, respectively. We present our basic formalism to
treat heavy particle mass effects to NLO in perturbative QCD. We also study
heavy quark effects on the QCD sum rule for the first moment of $g_1^\gamma$,
which is related to axial anomaly. The photon structure function in
supersymmetric QCD is also briefly discussed.
