PROBLEM TO BE SOLVED: To provide emulsifying agents which consist of core-corona type micro particles and whose emulsifying power is not influenced by a crosslinked level, and to provide oil-in-water emulsion cosmetics emulsified by the emulsifying agent.SOLUTION: A cosmetic raw material consisting of core-corona type micro particles is obtained by subjecting polyethylene oxide macro monomer and one or more hydrophobic monomers selected from a particular acrylate derivative monomer and a particular acrylamide-derivatives monomer, which have an (α-lower alkyl) acrylic ester group, to radical polymerization under particular conditions.SELECTED DRAWING: None【課題】架橋レベルによって乳化力が左右されないコア－コロナ型のミクロ粒子からなる乳化剤と、該乳化剤によって乳化された水中油型乳化化粧料の提供。【解決手段】（α－低級アルキル）アクリル酸エステル基を有する、ポリエチレンオキサイドマクロモノマーと、特定のアクリレート誘導体モノマー及び特定のアクリルアミド誘導体モノマーから選ばれる１種以上の疎水性モノマーとを、特定の条件でラジカル重合して得られるコア－コロナ型ミクロ粒子からなる化粧料用原料。【選択図】なし
