A process for producing polymer particles comprising polymerizing a water-soluble polymerizable monomer in a system comprising a hydrophobic organic solvent inert to the polymerization and an aqueous solution of the water-soluble polymerizable monomer, the process being characterized in that the polymerization is carried out in the presence of, as a dispersant, an anionic surface active agent represented by formula (I): ##STR1## wherein R.sup.1 represents a straight-chain or branched alkyl, alkenyl or 2-hydroxyalkyl group having 5 to 29 carbon atoms; M.sup.1 and M.sup.2, which may be the same or different, each represent an alkali metal ion, an ammonium ion or a hydrogen atom; and n represents 1 or 2.