Abstract: Carbon thin films with thickness of 100 nm were deposited on glass and silicon substrates at a substrate temperature of 20℃ by pulsed laser deposition (PLD) using a graphite target. The laser source used was an ArF excimer laser (λ= 193 nm, 24ns). The ambient pressure was changed between 1.33×10-5 Pa and 133Pa by adjusting the amount of hydrogen gas flow. The Raman spectrum measurement showed a broad peak with a center of 1550 cm-1, similar to those of the typical DLC films prepared using other methods. With increasing hydrogen pressure, the absorption coefficient decreased and the optical band gap increased. The films deposited at the hydrogen pressure of 133Pa had an optical band gap of more than 2.5 eV, which is twice as large as that of films deposited with no hydrogen atmosphere.Theseresults indicate that the hydrogen gas is effective for etching the sp2 bonding fractions. In PLD method, the ejected species from the target form the plasma, and the hydrogen molecules are expected to be decomposed into atomic hydrogen. This atomic hydrogen must play the role of etching the sp2 bonding fractions, as it does for the case of CVD method.