TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The structure having 2 or more condensed aromatic ring contained in the polycyclic aromatic unit, has a hetero atom having lone pair as condensed ring atom, and further contains hydrophilic functional group. The structure having 2 or more atoms connected by single bond contained in flexible structural unit, is a silicone structure or aliphatic hydrocarbon structure each optionally containing hetero atom. The acidic functional group is coupled to condensed polycyclic aromatic unit, and is a group formed by coupling sulfonic acid or phosphoric acid group to terminal of sulfonic acid, phosphoric acid or spacer structure. The hydrophilic functional group is a group formed by coupling a proton dissociative group such as hydroxyl or thiol group, to a cyclic functional group having resonating structure. The abundance ratio of hydrophilic functional group with respect to acidic functional group is 0.1-10.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The polymer principal chain containing hydrophilic functional group, further contains an unit (P) having hydrophilic functional group as repeating unit. Unit (P) has hydrophilic functional group and two or more condensed aromatic ring. The polyelectrolyte has repeating unit of formulae (1,2).R1=portion which forms principal chain structure of condensed polycyclic aromatic unit having condensed polycyclic aromatic group having two or more condensed aromatic ring, and optionally contains endocyclic hetero atom and non-aromatic condensed ring, R1 is optionally coupled to groups other than R2 and R3;R2=acidic functional group having pKa of 5 or less, and optionally contains spacer structure interposed between acidic functional group and R1;p=number of R2 coupled to R1 and is 1 or more;R3=hydrophilic functional group having pKa of 2 or more, and optionally contains spacer structure interposed between hydrophilic functional group and R1;q=number of R3 coupled to R1 and is 0 or more;R4=portion which forms principal chain structure of hydrophilic functional group unit, and consists of hydrophilic functional group having pKa of 2 or more, R4 is coupled to groups other than R5;R5=hydrophilic functional group having pKa of 2 or more, and optionally contains spacer structure interposed between hydrophilic functional group and R4;r=number of R5 coupled to R4 and is 0 or more;R6=portion which forms principal chain structure of flexible structural unit, and optionally contains structure of cyclic form or unsaturated bond in terminal or middle of chain of single bond which forms the principal chain structure, and monovalent group is optionally coupled in middle of the chain of single bond;A1-A3=single bond or divalent organic group;R1a=condensed polycyclic aromatic group having 2-15 condensed aromatic ring, and optionally contains endocyclic hetero atom and non-aromatic condensed ring;R2a=sulfonic acid, phosphoric acid or group formed by coupling sulfonic acid or phosphoric acid group to terminal of spacer structure;s=1 or more;R3a=hydroxyl, thiol, or group having aromatic group which forms R1a and integral resonating structure as spacer structure, and hydroxyl or thiol group coupled to the terminal;t,u=0 or more;R4a=aromatic group, optionally containing endocyclic hetero atom and non-aromatic ring, or hydrophilic functional group formed by coupling proton dissociative group to cyclic functional group having resonating structure;R5a=hydrophilic functional group formed by coupling proton dissociative group to cyclic functional group having resonating structure;andR6a=silicone structure optionally containing aliphatic hydrocarbon structure or hetero atom, and optionally contains structure of cyclic form or unsaturated bond in terminal or middle of aliphatic hydrocarbon structure or silicone structure, and monovalent group is optionally coupled in the middle of structure.When R4 consists of hydrophilic functional group having pKa of 2 or more, R5 does not exist. Preferred Property: The polyelectrolyte has degree of polymerization of 5-150000. EXAMPLE - A mixed solvent (in ml) (10) of acetonitrile-methylene chloride, 9-sulfo phebyl-2,3,7-trihydroxy-6-fluorone (0.5 g) and 60% straight mineral oil dispersion liquid of sodium hydride (0.13) were stirred in argon atmosphere for 30 minutes. 2,6- dichloro indophenol sodium-salt hydrate (0.45 g) was added to the reaction solution, and stirred at room temperature for 2 hours, to obtain solution (A). 1,6-hexanediol (0.184 g) and 60% straight mineral oil dispersion liquid of sodium hydride (0.13) were stirred in argon atmosphere for 30 minutes. The obtained reaction solution was added to solution (A), and stirred at room temperature for 2 hours. The resulting solution was poured into water (80), and the settled product was washed twice with acetone. Thus, polyelectrolyte (0.6 g) was obtained. A polymer electrolyte film was formed using the polyelectrolyte. The film had high proton conductivity, water retentivity, chemical stability, heat resistance, oxidation resistance, durability and tensile strength.