The luminescence and optical properties of ceria (CeO_2) nanoparticles irradiated by accelerated electrons with an energy of 10 MeV are investigated in this work. CeO_2 nanoparticles are prepared by the pulse electron evaporation of a ceramic target with vapor condensation of the evaporated material in a low-pressure gas on a NANOBIM-2 installation. The irradiation of CeO_2 nanopowders is found to cause the degradation of their luminescence and optical characteristics. The irradiation of a final aqueous suspension leads to the shift of a photoluminescence band toward the long wave range spectral range in comparison with the irradiation of a nanopowder. The catalytic-like behavior of CeO_2 nanoparticles interacting with hydrogen peroxide is analyzed, as well. Nanoparticles modified by the electron beam exhibit the deterioration of their enzyme-like activity.