Transformation of the chemical composition and electron structure of graphite oxide (GO) nanolayers as a result of their annealing in hydrogen has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. It is established that both the chemical composition and bandgap width of GO can be controlled by varying the temperature and duration of heat treatment. By this means, the properties of GO nanolayers can be smoothly changed from dielectric to semiconductor.