Provided are: a core-corona polymer particle excellent in emulsion stability and feeling of use, and a raw material for a cosmetic and an oil-in-water emulsion cosmetic comprising the particle. Certain embodiments of the present invention provides a core-corona polymer particle obtained by radical-polymerizing a polyethylene oxide macromonomer represented by formula (1) and one or two or more of hydrophobic monomers represented by formulas (2) and (3) under conditions (A) to (D).