Provided is a stable and clear aqueous solution, characterized by containing (3-{2-[4-isopropyl-2-(4-trifluoromethyl)phenyl-5-thiazolyl]ethy l}-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.).La presente invención proporciona una preparación líquida acuosa y estable que contiene ácido (3-{2-[4-isopropil-2-(4-trifluorometi l)fenil-5-tiazolil]etil}-5-metil-1,2-bencisoxazol-6-il)oxiacético o una sal farmacéuticamente aceptable del mismo como un ingrediente activo, y cloruro de benzalconio representado por la fórmula: [C6H5CH2N(CH3)2R)Cl en donde R es un grupo alquilo que tiene de 8 a 18 átomos de carbono.
