TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The ionic conductive polymer has ion exchange group-containing aromatic ring and the principal chain, and an aromatic ring in the side chain. The ionic conductive polymer has repeating units of formulae (1a-4a) containing ion exchange group and repeating units of formulae (1b-4b) which do not contain ion exchange group: -(Ar1-Z-Ar2-X)-, -(Ar3-Z'-Ar4-X'-Ar5-(Y'-Ar6)p-X')-, -((Ar7)q-X"-(Ar8)r-X")-, -(Ar9)-, -(Ar11-Z-Ar12-X)-, -(Ar13-Z'-Ar14-X'-Ar15-(Y'-Ar16)p-X')-, -((Ar17)q-X"-(Ar18)r-X")- and -(Ar19)-, respectively.Ar1-Ar9=bivalent aromatic group which may have an aromatic ring in principal chain and aromatic ring in side chain, containing ion exchange group;Z,Z'=CO or SO2;X,X',X"=O or S;Y'=direct bond or group of formula: -C(R1)(R2)-;p=0, 1 or 2;Ar11-Ar19=optionally substituted bivalent aromatic group as side chain;q,r=1, 2 or 3;andR1,R2=H, optionally substituted (1-10C alkyl, 1-10C alkoxy, 6-18C aryl, 6-18C aryloxy or 2-20C acyl).R1 and R2 may connect to form a ring. The ionic conductive polymer is a copolymer containing polymer segment(s) (A) having ion exchange group and polymer segment(s) (B) which do not have ion exchange group, or a block copolymer containing block (A) having ion exchange group and block (B) which do not have ion exchange group. The polymer electrolyte membrane has micro phase-separation structure containing a phase with a high density of the block (A) and a phase with a high density of the block (B). The block (A) has repeating unit of formula (4a'): -(Ar9)m-. The block (B) has repeating units of formulae (1b', 2b' or 3b'): -(Ar11-Z-Ar12-X)n-, -(Ar13-Z'-Ar14-X'-Ar15-(Y'-Ar16)p-X')n- or -((Ar17)q-X"-(Ar18)r-X")n-.m=5 or more;Ar9=bivalent aromatic group optionally substituted by fluorine, (un)substituted (1-10C alkyl, 1-10C alkoxy, 6-18C aryl, 6-18C aryloxy or 2-20C acyl);n=5 or more;andAr11-Ar18=bivalent aromatic group optionally substituted by 1-18C alkyl, 1-10C alkoxy, 6-10C aryl, 6-18C aryloxy or 2-20C acyl.The blocks (A,B) do not have a substituent containing halogen. The polymer electrolyte membrane is removed from the base material and surface treated. The support base material contains resin film.