There is provided a gel composition that can be suitably used as a thickener for cosmetic preparations and the like. A gel composition comprising a neutralized product of an alkyl-modified carboxyl group-containing polymer, which is a copolymer of monomers comprising 100 parts by mass of (meth)acrylic acid (a), 2.5 to 5 parts by mass of a (meth)acrylic acid alkyl ester (b) in which the alkyl group has 18 to 24 carbon atoms, and 0.1 part by mass or less of a compound (c) having two or more ethylenically unsaturated groups; and at least one of an anionic emulsifier and a nonionic emulsifier.