PURPOSE: To obtain a high-nonvolatile content, low-viscosity, stable emulsion polymer, by polymerizing a comonomer containing a (meth)acrylate ester or styrene by adding a chain transfer agent immediately after forming polymer micelles by the use of hydroxyethylcellulose.

CONSTITUTION: Polymer micelles are formed by adding, before starting polymerization, part or the whole hydroxyethylcellulose to a mixture of at least one member selected from the group consisting of an acrylate ester, a methacrylate ester and styrene and another monomer copolymerizable therewith, and starting the polymerization of the resulting mixture in the absence of a chain transfer agent with the aid of water, an emulsifier and a polymerization catalyst. Immediately after the formation of polymer micelles, a chain transfer agent is added. Then the heat of polymerization is slowly removed by continuous dropwise addition of water, an emulsifier, etc., to the remaining monomer. After completion of the addition, the remaining monomer is converted to polymer under aging to heighten the conversion to above about 99%.