The present invention is a core corona type microgel emulsifier formed from a copolymer obtained by polymerizing a polyethylene oxide macromonomer a hydrophobic monomer and a cross linking monomer under specific conditions. The present invention is also an oil in water emulsion composition characterized in that the core corona type microgel emulsifier is used to emulsify the oil in water emulsion composition. The purpose of the present invention is to provide a novel core corona type microgel emulsifier used for producing an oil in water emulsion composition which exhibits excellent emulsion stability and temporal stability causes little skin irritation or feeling of coarseness is not powdery or sticky when applied is fresh and exerts an aroma sustaining effect. Another purpose of the present invention is to provide an oil in water emulsion composition which is emulsified by means of the aforementioned emulsifier.
