To provide a polymer of a new family for controlling rheology of an aqueous composition as a function of temperature while keeping transparency of the aqueous composition at a level that is useful as a composition for cosmetics or pharmaceuticals.

The aqueous composition comprises a polymer or one of salts of the polymer, and the polymer comprises a water-soluble unit carrying at least two reactive sites and a unit carrying at least one reactive site capable of reacting with the reactive sites carried on the water-soluble units to form a covalent bond and having a lower critical solution temperature (LCST), wherein, the units having the LCST are a random copolymer of ethylene oxide and propylene oxide having an ethylene oxide number of 0-40 and a propylene oxide number of 15-60. In addition, the aqueous composition is also an especially thickened or even gelated one containing such a polymer or one of its salts and an aqueous phase.