The magneto-optic Kerr angle spectrum of a single crystal of MnBi was measured at room temperature and also calculated with the TB-LMTO methods including the spin-orbit interaction. First-principle calculations and experimental results with our single crystal MnBi were compared. The complex dielectric constants and magneto-optic Kerr spectra of electro-polished (100), (110), and (111) planes Ni2MnGa were measured. Also optical and magneto-optical spectra were calculated with the TB-LMTO methods including the spin-orbit interaction. Angle-dependent reflectance difference spectroscopy of Gd5Si2Ge2 and Tb5Si2.2Ge1.8, which are optically anisotropic materials, were measured with the Kerr spectrometer by rotating the samples. The complex dielectric constants of (100) and (001) planes Gd5Si2Ge2 were measured by the spectroscopic ellipsometer. Two reflectance differences, measured by the Kerr spectrometer at near normal incidence and converted from the dielectric constants measured by ellipsometer at oblique incidence, agreed well.