NOVELTY - A metal roll electrode is worked with a base material, a mixed gas of nitrogen, helium and/or argon is introduced in process space provided between ground electrodes, and pressure in process space is adjusted. High frequency voltage is applied to process space, and high-density plasma is generated. A plasma surface-treated layer is formed on the surface of base material. High-density plasma is collided with evaporating particles, and particles are activated. A gas barrier layer (102) containing silicon oxide is formed on surface-treated layer. Thus, gas barrier film (120) is formed.    USE - Manufacture of gas barrier film (claimed) for packaging material of foodstuff and pharmaceuticals, and protection sheet of solar cell.    ADVANTAGE - The gas barrier film is manufactured with high gas barrier property.    DETAILED DESCRIPTION - A metal roll electrode is worked with a base material, a gas obtained by mixing nitrogen, helium and/or argon is introduced in process space provided between ground electrodes arranged along metal roll electrode, and pressure in process space is adjusted to predetermined range of 0.5-50 Pa. High frequency voltage of more than 30 kHz and less than 4 kHz is applied to the process space, and a high-density plasma is generated in the process space. A plasma surface-treated layer is formed on the surface of base material. High-density plasma is collided with evaporating particles formed by vacuum evaporation method, and evaporating particles are activated. A gas barrier layer containing silicon oxide (SiOx, x is 1-2.2) is formed on plasma surface-treated layer. The shortest distance of metal roll electrode and ground electrode is 50 mm or less. Thus, a gas barrier film is formed. The high-frequency voltage is applied such that the value calculated from product of processing time and electric power density computed from electric power supplied to metal roll electrode or ratio with area of processing or opening portion of metal roll electrode, is made into more than predetermined value.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of gas barrier film.    Plastic film (100)    Adhesion processing layer (101)    Gas barrier layer (102)    Protective layer (103)    Gas barrier film (120)