PURPOSE: To prevent the title permselective membrane from being charged and to obviate the deterioration in the performance due to static electricity by forming ≥1 layer of the composite membrane with an electrically conductive layer.

CONSTITUTION: A conductive layer is provided on the back of at least a porous supporting membrane of the composite membrane consisting of the porous supporting membrane and a functional membrane. A material consisting essen tially of a surfactant is used for the conductive layer, and the surface resistivity is controlled to ≤1×1010Ω. Any porous formed article can be used as the porous supporting membrane, and the microporous supporting membrane having 0.005W0.1μ pore diameter and permeable to air is preferably used. A material capable of separating a gaseous and liq. material to be separated, especially capable of separating an oxygen/nitrogen mixture, is used as the functional membrane. Since the conductive layer is brought into contact with the functional membrane surface when the composite membrane is wound, the layer of the surfactant is preferably used as the conductive layer, because the functional membrane is not damaged by such a conductive layer and the gas separability is not deteriorated.