  We calculate the ${\cal O}(\alpha_{s})$ QCD and ${\cal O}(\alpha_{{\rm ew}})$
electroweak one-loop corrections in the Standard Model framework, to the
production of an intermediate Higgs boson associated with $t\bar{t}$ pair via
$\gamma \gamma$ fusion at an electron-positron linear collider (LC). We find
the ${\cal O}(\alpha_{s})$ QCD corrections can be larger than the ${\cal
O}(\alpha_{{\rm ew}})$ electroweak ones, with the variations of the Higgs boson
mass $m_{h}$ and $e^+e^-$ colliding energy $\sqrt{s}$. Both corrections may
significantly decrease or increase the Born cross section. The numerical
results show that the relative corrections from QCD to the process \eep may
reach 34.8%, when $\sqrt{s}=800$ GeV and $m_h=200$ GeV, while those from
electroweak can be -13.1%, -15.8% and -12.0%, at $\sqrt{s} = 800$ GeV, 1 TeV
and 2 TeV respectively.
