NOVELTY - A sulfonic acid group-containing polymer is obtained by co-polymerizing a monomer component containing a specific siloxane monomer (A), and a monomer (B) having unsaturated polymerizable group and sulfonic acid group.    USE - For polymer composition (claimed) used for coating material of non-woven fabric used for battery separator, ion exchange membrane, solid polymer electrolyte used for fuel cell, modifier, humidity control material, such as air cleaning filter, stain resistant material, water purifying filter, antimicrobial material, water vapor pervious material, deodorizing coating material, deodorant paper, fog prevention material, filter for leukopheresis, pollinosis allergen removal material, dew formation prevention material, anti-corrosion material, oxygen absorbent, sanitary products, photograph material, floor polishing material, masking material, size material for paper, paper-strength increasing material, adhesive agent, silver-halide photosensitive material, electromagnetic shielding material, antistatic coating material, planar heating element, electrochemical reaction electrode plate, sliding material, electric contact material, magnetic recording medium, thermosensitive recording material, electrochromic material, light diffusion film, water barrier material for telecommunication cable, sound insulation sheet, printing ink, and electrophotographic toner.    ADVANTAGE - The sulfonic acid group-containing polymer has reduced volume resistivity and excellent carbon dispersibility.    DETAILED DESCRIPTION - A sulfonic acid group-containing polymer is obtained by co-polymerizing a monomer component containing a silicon-containing monomer (A) of formula (1), and a monomer (B) having unsaturated polymerizable group and sulfonic acid group.    A=unsaturated polymerizable group;    X=1-10C hydrocarbon group;    R1-R6=group of formula (2), alkyl group optionally substituted with fluorine atom, phenyl, vinyl or hydrogen atom, and all R1-R6 are not hydrogen;    Z=-X-B' or fluoro alkyl group;    X=1-10C hydrocarbon group;    B=unsaturated polymerizable group or hydrogen atom;    k=0-100;and    Y1-Y3=alkyl group optionally substituted with fluorine atom, phenyl, vinyl or hydrogen atom, and two or more Y1-Y3 are not hydrogen atom.    INDEPENDENT CLAIMS are included for the following:    (1) manufacture of sulfonic acid group-containing polymer, which involves copolymerizing monomer component in solvent containing methanol as a main component; and    (2) polymer composition, which contains sulfonic acid group-containing polymer (20-80 mass%) and polyorganosiloxane-containing polymer (20-80 mass%) with respect to 100 mass%.    DESCRIPTION OF DRAWING(S) - The graph shows the relationship between weight average molecular weight of polymer composition with respect to holding time. (Drawing includes non-English language text)