The purpose of this research is to elucidate the effect of the emulsifier on the dynamic behavior of particle size distribution (PSD) in continuous emulsion polymerization. Emulsion polymerization of vinyl acetate was performed in a continuous stirred tank reactor. An anionic surfactant (sodium dodecyl sulfate: SDS) was used as an emulsifier. The initial emulsifier concentration in the reactor and that in the feed was varied as a control parameter. In order to vary the colloidal stability of latex particles, a nonionic surfactant (polyoxyethylene sorbitan monooleate: Tween80) was added in some cases. It has been found that PSD varies with time even while the constant monomer conversion is maintained at a steady state in all cases. Compared with the case of using only SDS, however, using a mixture of anionic surfactant and nonionic surfactant can effectively suppress this time-dependent behavior.