Theoretical investigation has been performed on the Faraday effect of Cd_<1-x>Mn_xTe epitaxial films prepared by the ionized-cluster beam (ICB) deposition technique. Splitting energies and oscillator strengths of an exciton level are calculated by taking account of a nondegenerate second order perturbation. The wavelength dispersion of the calculated Faraday rotation spectra is compared with the experimental data of Cd_<1-x>Mn_xTe films. This suggests that the Faraday rotation is closely related to the magneto-optical transitions to Zeeman splitting levels of exciton.