[en] We investigated the structural and the optical properties of ZnO thin films formed on Corning glass by the oxidation of Zn thin films, which were deposited by using thermal evaporation and were then oxidized at 300 − 600 ◦C. The grain size of the ZnO thin films increased and the grains became more densely packed with increasing oxidation temperature. In the photoluminescence (PL) spectra of the ZnO thin films, the intensity of the near-band-edge peak increased with increasing temperature to 500 ◦C, but decreased gradually with further increases in the temperature. The transmittances of the ZnO thin films formed by oxidation at 400 and 500 ◦C were higher than 85% in the visible-light region. Finally, the Urbach energy decreased significantly and the optical band gap exhibited a blue shift with increasing oxidation temperature from 300 to 400 ◦C.