A strongly acidic cation exchanger is obtained by sulfonating bead polymer formed from aromatic vinyl monomer, crosslinker and vinyl ether and/or vinyl ester (0.2-20 weight%). An independent claim is included for manufacture of strongly acidic cation exchanger, which involves preparing mono-dispersed or hetero-dispersed bead polymer from vinyl aromatic monomer, crosslinker and vinyl ether and/or vinyl ester by suspension polymerization and converting bead polymer by the action of sulfuric acid, sulfur trioxide and/or chlorosulfonic acid.
