An asymmetric hollow-fiber gas separation membrane is made of a soluble aromatic polyimide that is composed of a specific repeating unit. The tetracarboxylic acid component of the unit has a diphenylhexafluoropropane structure and a biphenyl structure. The diamine component of the unit essentially contains diaminobenzoic acids and any of diaminodibenzothiophenes, diaminodibenzothiophene=5,5-dioxides, diaminothioxanthene-10,10-diones, and diaminothioxanthene-9,10,10-triones.