Spectroscopic ellipsometry was used for the characterization of ion-deposited diamond-like carbon (DLC) films, including the determination of film thickness and optical properties of DLC. The measured spectra in the wavelength range from 300 to 850 nm were analyzed with an appropriate fitting model, which was constructed according to the nominal sample structure in which the optical properties of DLC were described by a Cauchy dispersion model. Reasonably good agreement was found between the measured and calculated spectra for all samples studied, indicating that the models used were appropriate and that the calculated results were reliable. The results of our analysis suggest that, under the same deposition conditions (i.e., same substrate temperature and same chamber pressure), the optical properties of ion-deposited DLC film did not change much even if the film was prepared with quite different gas flow ratios.