PURPOSE: To obtain the titled film having improved properties of separation, permeability and durability by providing a layer A made of a high polymer and having a gas permeability, and a layer B made of a polyarylene oxide contg. a silicon atom on a porous substrating body.

CONSTITUTION: The layer A made of the high polymer and having the gas permeability and the layer B made of the polyarylene oxide and contg. the silicon atom are provided on the porous substrating body to form the composite film for the gas separation. The material constituting the porous substrating body contains a polysulfonic acid or a polyolefins, etc. Size of fine pores lying on the surface of the substrating body is preferably 10W2,000. The oxygen permeability coefficient PO2 of the layer A is preferably 1×10-8(cm2.cm/ cm2.sec.cm Hg). The layer B is made of the polyarylene oxide contg. the organosilyl group.