To provide a gas barrier molding in which low temperature treatment can be performed without using an expensive vacuum device by using a silazane compound, and gas barrier performance equal to that of a silica membrane obtained by an evaporation method is imparted to a synthetic resin molding.

The gas barrier molding has the synthetic resin molding 1 and the silica membrane which is formed at part or the whole of the surface of the synthetic resin molding, the silica member uses the silazane compound as a precursor, and the gas barrier molding is formed by applying ultra-ray irradiation and heat treatment to the silazane compound simultaneously.