  We present the effects of heavy CP-even (H) and CP-odd (A) Higgs bosons on
the production cross section of the process $\gamma\gamma$ $\to t\bar{t}$ at
the energy around the mass poles of the Higgs bosons. It is found that the
interference between H and A with the small mass gap, as well as the ones
between Higgs bosons and the continuum, contributes to the cross section, if
the photon beams are polarized and if we observe the helicity of the top
quarks. It is demonstrated in the framework of the minimal supersymmetric
extension of the standard model that the H and A contributions can be sizable
at future $\gamma\gamma$ colliders for small value of $\tan\beta$. The methods
to measure the CP-parity of the Higgs boson are also presented. The statistical
significances of detecting the Higgs signals and measuring the Higgs CP-parity
are evaluated.
