To provide an ionic water-soluble polymer requiring less transportation cost and imposing less environmental burden, a process for producing it, and its usage as a coagulating agent, more particularly, to provide an ionic water-soluble polymer exhibiting excellent performance in dehydration of polluted sludge, in dehydration of papermaking sludge, and in a papermaking process by adding it to a paper stock.

The problem is solved by providing an ionic water-soluble polymer which comprises powder exhibiting a particular ionic characteristic. The ionic water-soluble polymer is produced by emulsification and polymerization wherein a water-immiscible organic liquid becomes a continuous phase and an aqueous solution of monomer mixture essentially containing a cationic monomer and a polyfunctional monomer with plural unsaturated double bonds becomes a disperse phase by means of a surfactant, followed by granulation of the resulting water-in-oil emulsion after a drying step.