Provided is a stable and clear aqueous solution, characterized by containing (3-{2-[4-isopropyl-2-(4-trifluoromethyl)phenyl-5-thiazolyl]ethyl}-5-methyl-1,2-benzisoxazole-6-yl)oxyacetic acid or a pharmaceutically acceptable salt thereof as an active component, and by being formulated with a benzalkonium chloride represented by the formula [C6H5CH2N(CH3)2R]Cl (in the formula, R is an alkyl group with 8-18 carbon atoms.).
