NOVELTY - Gas barrier film has a silicon oxide film composed of the rate of components that the number of oxygen atoms is 170-200 and the number of carbon atoms is 30 or less to the number of silicon atoms of 100, and has a peak position of infrared carbon atoms band based on the stretching vibration of silicon-oxygen-silicon that exists at 1055-1065 /cm.    USE - As packing material for food and medicines, and as packaging material for electronic devices. It can also be used as base material for, e.g. displays, and in cover films for solar cells.    ADVANTAGE - The invention has an extremely excellent gas barrier property while retaining the film thickness at a predetermined thickness.    DETAILED DESCRIPTION - A gas barrier film has a silicon oxide film formed by plasma chemical vapor deposition method on one side or both sides of a base material. The silicon oxide film is composed of the rate of components that the number of oxygen atoms is 170-200 and the number of carbon atoms is 30 or less to the number of silicon atoms of 100, and has a peak position of infrared carbon atoms band based on the stretching vibration of silicon-oxygen-silicon that exists at 1055-1065 /cm. INDEPENDENT CLAIMS are also included for:    (I) a method for producing a gas barrier film comprising using at least an organic silicon compound gas and a gas containing oxygen atoms as raw material gases, and forming silicon oxide film on a base material by plasma CVD method within a reaction chamber;    (II) a laminated material comprising a heat sealable resin layer or an electrically conductive layer provided on the surface of at least one side of the gas barrier film;    (III) a packaging container comprising the laminated material with the heat sealable resin being heat sealed to make a bag or case; and    (IV) an image display medium comprising an image display layer being formed on the electrically conductive layer using the laminated material as base material.    A component on the organic silicon compound gas is a compound that has no carbon-silicon bond in its molecule. The base material is at -20 to 100 degrees C at the start of film forming. The silicon oxide film is formed at the flow ratio of the gas containing oxygen atoms to organic silicon compound gas of 3-50 when the organic silicon compound gas is 1. The film is heat treated at 50-200 degrees C.