TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The usage amount of organic solvent is 20 wt.% or more.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The ionic conductive aromatic polymer is a block copolymer having a polymer segment (A) which contains ionic conduction component having sulfonic acid group or phosphoric acid group, and polymer segment (B) which does not contain the ionic conduction component. The ionic conductive aromatic polymer has structure in which aromatic ring is covalently bonded with the bonding group, in its principal chain. The ionic conductive aromatic polymer is polyarylene containing sulfonic acid group-containing structural unit of formula (A) and structural unit derived from benzene, of formula (B).Y=-CO-, -SO2-, -SO-, -CONH-, -COO-, -(CF2)l- or -C(CF3)2-;l=1-10;Z=direct bond, -(CH2)l-, -C(CH3)2-, -O- or -S-;Ar=aromatic group having -SO3H, -O(CH2)pSO3H or -O(CF2)pSO3H as substituent;p=1-12;m,n=0-10;k=1-4;A,D=direct bond, -CO-, -SO2-, -SO-, -CONH-, -COO-, -(CF2)l-, -CR'2, cyclo hexylidene, fluorenylidene, -O- or -S-;R'=aliphatic hydrocarbon, aromatic hydrocarbon or halogenated hydrocarbon;Q=oxygen atom or sulfur atom;R1-R16=H, fluorine atom, halogenated alkyl, partially halogenated alkyl, allyl, aryl, nitro or nitrile;s,t=0-4;andr=0 or 1 or more. EXAMPLE - Neopentyl 3-(2,5-dichlorobenzoyl) benzene sulfonic acid (in g) (119), hydrophobic unit (30.4) of formula (I) having number average molecular weight of 7800, bis(triphenyl phosphine) nickel dichloride (5.89), sodium iodide (1.35), triphenyl phosphine (31.5) and zinc (47.1), were mixed, and N,N-dimethylacetamide (700 ml) was added. Dimethyl acetamide (350 ml) was added and stirred for 3 hours at 80degreesC. Insoluble contents were filtered, and the obtained solution was heat-stirred at 115degreesC. Lithium bromide (56.6) was added and stirred for 7 hours. Acetone (5 l) was added, and washed with 1 N hydrochloric acid and pure water. The reaction mixture was filtered and a sulfonated polymer was obtained. The obtained polymer had weight average molecular weight of 260000 and ion exchange capacity of 2.3 meq/g. YTZ ball (RTM: zirconia ball) (25), platinum carrying carbon particles (1.53), distilled water (0.88), N-methyl-2-pyrrolidone (12.47), 15 wt.% N-methyl-2-pyrrolidone solution of the sulfonated polymer (II) (4.59) and VGCF (RTM: gaseous phase carbon fiber) (0.7), were mixed and stirred for 30 minutes. A paste (A) was obtained. The obtained paste was applied on a carbon paper and dried at 120degreesC for 60 minutes. An electrode catalyst layer having platinum content of 0.5 mg/cm2 was formed. The obtained catalyst layer prevented generation of crack and pinhole.