  We calculate the cross section of Higgs boson pair production at a photon
collider in the two Higgs doublet model. We focus on the scenario in which the
lightest CP even Higgs boson ($h$) has the standard model like couplings to the
gauge bosons. We take into account the one-loop correction to the $hhh$
coupling as well as additional one-loop diagrams due to charged Higgs bosons to
the $\gamma\gamma\to hh$ helicity amplitudes. It is found that the full cross
section can be enhanced by both these effects to a considerable level. We
discuss the impact of these corrections on the $hhh$ coupling measurement at
the photon collider.
