Applicability of self-consistent-charge density-functional tight-binding method with dispersion correction (SCC-DFTB-D) was tested to the graphene adsorption of medium-sized molecules. We computed adsorbed structures of transition-metal complexes of porphyrin and porphycene on graphene, and evaluated the adsorption energies. The energies reasonably corresponded to the reference values evaluated by density functional theory (DFT) calculations. Furthermore, we confirmed the model size dependence of energy less than 1 kcal mol(-1) by expanding the graphene size. SCC-DFTB-D can be an alternative choice for the computation of graphene adsorption of large molecules that are out of scope for typical DFT in terms of the computational cost.