A simple deposition system using cw CO2 laser for preparation of polysiloxane thin films was demonstrated. Polysiloxane bulk target was evaporated by using CO2 laser irradiation. During him deposition, remote microwave plasma as a radical source was utilized in order to improve the hardness of formed polysiloxane film. Oxygen (O-2) gas or water vapor (H2O) was used as a source of reactive species for surface modification of polysiloxane film. The effects of radicals produced by the microwave O-2 or H2O plasma on the properties of polysiloxane films were investigated using x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography analyses. Using this system, polysiloxane thin films, of which the chemical structure and composition were close to those of polysiloxane bulk target, were successfully prepared. The molecular weight of the film was about 40 000, which was larger by a factor of 20 than the value of 2100 of the bulk target.