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.本發明係關於一種冠狀核型微凝膠乳化劑，係由特定之條件下使聚環氧乙烷巨分子單體(polyethylene oxide macromonomer)、疏水性單體及交聯性單體進行聚合而獲得之共聚物所構成；及一種水中油型乳化組成物，係使用該冠狀核型微凝膠乳化劑及該乳化劑進行乳化而成。本發明之目的在於提供一種用於製造具有優異之乳化穩定性、經時穩定性、低皮膚刺激性，無塗抹時之黏性，水潤而無粉末感或粗糙感，進而香味之持續效果亦優異之水中油型乳化組成物的新穎之冠狀核型微凝膠乳化劑；及利用該乳化劑進行乳化而成之水中油型乳化組成物。
