A gas separating material having excellent CO.sub.2 gas permeating property, mechanical property, and heat resistance has a gas separating layer comprising an aromatic imide polymer which contains 20 to 100 molar % of recurring units of the formula (I): ##STR1## wherein A.sub.1 is a tetravalent aromatic radical, A is a divalent aromatic radical of the formula (II): ##STR2## in which R and R.sup.1 are H or an organic radical, for example, --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7, or --CH.sub.2 OH, and n is 0, 1, or 2.