PURPOSE: To obtain a self-dispersed water-based resin which is uniform and stable and has a small particle diameter, by forming a polymer solution from an monomer having a salt-forming group and a polymerizable double bond, a copolymerizable monomer having a polymerizable double bond and a hydrophilic organic solvent and converting this polymer solution into a water- based dispersion.

CONSTITUTION: A polymer solution is obtained by solution-polymerizing 2W25wt% monomer having a salt-forming group and a polymerizable double bond with 98W75wt% copolymerizable monomer having a polymerizable double bond in a hydrophilic organic solvent or by bulk-polymerizing said monomers and dissolving the bulk-polymerized polymer in a hydrophilic organic solvent. This polymer solution is converted into a water-based dispersion by ionizing the salt-forming groups by the addition of, if necessary, a neutralizing agent, adding water to the solution and removing the hydrophilic organic solvent. As said organic solvent, at least one of the alcohol, ketone, ester and ether solvents is desirably used.