PURPOSE: To obtain a high water vapor permeating flow speed with a small vapor pressure difference as a reproducer by a method wherein ion near a charged film is excluded to increase the partial pressure of water and enlarge the difference of vapor pressures at both sides of a hydrophobic porous film by forming a charged film on the hydrophobic porous film.

CONSTITUTION: A film module, accommodated in a reproducer, is made by molding a material, in which a charged film is formed on a hydrophobic porous film. The charged film is obtained by a method wherein the base material is received in the reaction vessel of a plasma graft polymerizing device and the vessel is evacuated, then, low-temperature plasma is emitted to generate free-radiacl and, thereafter, 5% acrylic acid solution in a monomer vessel is contacted while evacuating it in a liquid phase, then, the reaction vessel is polymerized in an always high-temperature tank through graft polymerization. According to this method, the permeating flow speed of a film, obtained on No.3 polyethylene porous film through plasma polymerization, becomes higher compared with a polyethylene porous film of a hydrophobic porous film so far. Accordingly, a vapor pressure difference, which becomes the driving force of permeation, is permitted to be reduced and the increase of the amount of permeation can be permitted.