SiO2 films were prepared by an ion-beam sputtering (IBS) method and their properties were studied using visible-UV absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and IR transmission spectroscopy, The SiO2 films prepared with O-2 atmosphere had good transparency in the visible region. Only the XPS signal due to the Si-O-2 bond was observed, and the film composition was almost stoichiometric. However, the full widths at half maximum of the XPS peak and each IR band of the SiO2 films were larger than those of thermally oxidized SiO2 films. This suggests that the SiO2 films prepared by the IBS were more disordered than the thermally oxidized SiO2 films. The IR spectra showed that the structure of the SiO2 films prepared by the IBs method was mainly coesite like and was different from that of the thermally oxidized SiO2 which was mainly quartz like.