NOVELTY - At least one of aromatic dihalogen compound, specific dihydric phenol compound and specific bivalent thiophenol compound having ionic group is polycondensed in an organic polar solvent in the presence of an alkali metal compound, and polymerized in a reaction vessel at 180-230degrees C. Water is produced as byproduct during alkali metal salt reaction of phenol group or thiophenol group. Water is distilled off at specific conditions and removed. Polymer having aromatic ether structure and/or aromatic sulfide structure is manufactured.    USE - Manufacture of ionic group-containing polymer for polymer electrolyte membrane such as electrolysis film and separation membrane used for membrane-electrode assembly used for fuel cell (all claimed), such as direct methanol fuel cell.    ADVANTAGE - The ionic group-containing polymer is easily manufactured with high molecular weight and without generation of gelatinization and solidification using simple installation. The polymer has favorable bondability with electrode.    DETAILED DESCRIPTION - At least one of aromatic dihalogen compound, dihydric phenol compound and bivalent thiophenol compound having ionic group is polycondensed in an organic polar solvent in the presence of an alkali metal compound, and polymerized in a reaction vessel at 180-230degrees C. Water is produced as byproduct during alkali metal salt reaction of phenol group or thiophenol group. Water is distilled off with organic polar solvent in air flow or inert gas atmosphere at temperature from boiling point of polar solvent to temperature less than boiling point of organic polar solvent by 20degrees C, and removed. Polymer having aromatic ether structure and/or aromatic sulfide structure is manufactured. At least one of dihydric phenol compound and bivalent thiophenol compound has structure of formula (1). The organic polar solvent is mixed solvent of water, is liquid at normal temperature, and has boiling point of 200degrees C or more under normal pressure.    Z1=group derived from OH and SH;    Z2=oxygen atom, sulfur atom, -C(CH3)2- group, -C(CF3)2- group, -CH2- group or cyclohexyl group;and    n=0 or more.    DESCRIPTION OF DRAWING(S) - The drawing shows the polymerization apparatus.    Stirring motor (1)    Stirring blade (2)    Jacket heater (3)    Reaction container (4)    Nitrogen inlet tube (5)