The present invention provides a stable and clear aqueous liquid preparation containing (3-{2-[4-isopropyl-2-(4-trifluoromethyl)phenyl-5-thiazolyl]ethyl}-5-methyl-1,2-benzisoxazol-6-yl)oxyacetic acid or a pharmaceutically acceptable salt thereof as an active ingredient, and benzalkonium chloride represented by the formula: €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ[C 6 H 5 CH 2 N(CH 3 ) 2 R]Cl wherein R is an alkyl group having 8 - 18 carbon atoms.