A hydrophilic thickener comprising a polymer obtainable by subjecting a water-soluble ethylenically unsaturated monomer to a reversed phase suspension polymerization in the presence of a polyoxyethylene polyoxypropylene alkyl ether; and a cosmetic composition containing the hydrophilic thickener. The hydrophilic thickener according to the present invention can be used in the fields of cosmetics such as powder foundations, liquid foundations, emulsions, lotions, liquid cosmetics, moisturizing gel, all-in-one gels, cleansing foams, hair setting agents, emollient creams; toiletries, sundries, and the like.