To provide a gas separating membrane and a composite membrane excellent in a gas permeability and a separation selectivity, and to provide their manufacturing method, a method for separating a gas mixture, module using it, and a separator.

The gas separating membrane contains a polymer containing at least a partial structure expressed by the following general formula (I) and at aleast a partial structure expressed by the following general formula (II): (I) [CH2C(R1)(J1W1Ra)](II)[CH2C(R2)(J2W2)]nL1 (wherein R1, R2 or Ra is each independently a hydrogen atom or a saturated group; L1 is a linking group of n valence; W1 and W2 are a single bond or a linking group of bivalence; n is two or more integers; J1, W1, R1, J2, W2, R2 and Ra existing plurally may be the same or different). At least one of Ra of the general formula (I) and of L1 of the general formula (II) has a fluorine atom.