An aqueous composition containing 2-amino-3-(4-bromobenzoyl)phenylacetic acid or a salt thereof, benzalkonium bromide, and polyoxyethylene sorbitan fatty acid ester wherein the stability of the 2-amino-3-(4-bromobenzoyl)phenylacetic acid in the aqueous composition is improved by limiting the content of benzalkonium bromide and polyoxyethylene sorbitan fatty acid ester to a certain range.