To provide an emulsion excellent in water dispersibility and mechanical stability in a low molecular weight without causing a problem of a bad smell, while a control of the molecular weight is easy.

The production method of the emulsion comprises a process (A), a process (B) and a process (C). Wherein, (A) means the process which a radical polymer is obtained by radicalpolymerized a mixture of monomers mainly composed of 5 mol% or more monomer containing a carboxyl group and a monomer containing a styrene monomer and a methacrylate in the presence of MSD. (B) means the process which a micromonomer containing an ethylenic unsaturated group is obtained by radicalpolymerized a mixture of monomer (b) mainly composed of a styrene monomer or a monomer containing a methacryloyl group, and a mole fraction of a monomer containing a carboxyl group is lower than that of the mixture of the monomer (a) in the presence of the radicalpolymer, (C) means the process which emulsion polymerizes an ethylenic unsaturated compound in the presence of the micromonomer.