  In this paper, we present general one-loop form factors for $H\rightarrow
\gamma^* \gamma^*$ in $R_{\xi}$ gauge, considering all cases of two on-shell,
one on-shell and two off-shell for final photons. The calculations are
performed in standard model and in arbitrary beyond the standard models which
charged scalar particles may be exchanged in one-loop diagrams. Analytic
results for the form factors are shown in general forms which are expressed in
terms of the Passarino-Veltman functions. We also confirm the results in
previous computations which are available for the case of two on-shell photons.
The $\xi$-independent of the result is also discussed. We find that numerical
results are good stability with varying $\xi=0,1$ and $\xi\rightarrow \infty$.
