Abstract: A permeable polymer membrane, formed of a fluorine type copolymer containing a repeating unit represented by the general formula: ##STR1## wherein m is 0 or 1 and n is an integer of the value of 2 to 5 and satisfying the relation between the water absorption ratio, W, and the ion-exchange capacity, Q, represented by the following formula:1.20Q-1.964<log W<1.2=0Q-1.742wherein W is W.sub.2 -W.sub.1)/W.sub.1, W.sub.1 a dry weight, W.sub.2 an equilibrium weight as immersed in pure water at 25.degree. C., and Q an ion-exchange capacity in meq/g of H form dry resin. This permeable polymer membrane is capable of highly desiccating a gas to a low water content. By the use of the extremely desiccated gas, semiconductor elements, semiconductor devices, intermediates thereof, and new components can be produced with outstanding quality. This permeable polymer membrane can be produced by a heat treatment.