The effectiveness of ozone incorporation in reactive gas of oxygen for producing indium oxide films by DC reactive magnetron sputtering employing a metal target has been investigated. It was found that 4% volume concentration of O-3 in addition to oxygen greatly enhanced the reactivity of the sputtered particles on the substrate of growing surface without substrate heating. The deposition rate of stoichiometric oxide film is found much greater in ozone added environment than that of growing in only oxygen environment.