To provide an emulsifier comprised of core-corona type microparticles that emulsification capability thereof is not affected by the crosslinking level and an oil-in-water emulsified cosmetic emulsified by the afore-mentioned emulsifier.A cosmetic raw material comprising:a core-corona type microparticles that is obtained by radical polymerization of a polyethylene oxide macromonomer represented by a chemical formula (1), and at least one hydrophobic monomer selected from a group of an acrylate derivative monomer represented by a chemical formula (2) and an acrylamide derivative monomer represented by a chemical formula (3) under the following conditions (A) to (D)；(A) a molar ratio expressed by a feed molar amount of the polyethylene oxide macromonomer/a feed molar amount of (the acrylate derivative monomer and/or the acrylamide derivative monomer) is 1:10 to 1:250；(B) the macromonomer represented by the chemical formula (1) is at least one derivative selected from a group consisting of an acrylic acid derivative and a methacrylic acid derivative that have a polyethylene glycol group with 8 to 200 repeating units,the acrylate derivative monomer represented by the following formula (2) is at least one monomer selected from a group consisting of an acrylic acid derivative and a methacrylic acid derivative that have a substituent comprising an alkyl group having 1 to 12 carbon atoms, and the acrylamide derivative monomer represented by the chemical formula (3) is at least one monomer selected from a group consisting of an acrylamide derivative and a methacrylamide derivative that have a substituent comprising an alkyl group having 1 to 18 carbon atoms；(C) a polymerization solvent is a mixture of alcohol and water,wherein the alcohol is at least one alcohol selected from a group consisting of ethanol, dipropylene glycol, 1,3-butylene glycol and isoprene glycol； and(D) a solvent composition of the water-alcohol mixed solvent is water:alcohol = 90 to 10:10 to 90 in a mass
