PURPOSE: To obtain the title membrane having a high gas permeation coefficient by copolymerizing the compd. shown by a specified formula and NH2-CH2-CH= CH2, adding (H3C)3SiH to the allyl group part of the obtained polymer, and forming the polymer into a membrane.

CONSTITUTION: The hydrocarbonic compd. modified with a nonaromatic epoxy group on both terminals and shown by the general formula I and the primary monoamine shown by NH2-CH2-CH=CH2 are mixed in an equimolecular ratio, and (H3C)3SiH is added to the allyl group part of the obtained epoxy polymer to form a silylated epoxy polymer. The obtained polymer is spread over a water surface, etc., and formed into a membrane. The obtained membrane has a high gas permeation coefficient and high O2/N2 selectivity, and its physical strength is also increased.