A method of producing Ethyl(3R,5S,6E)-7-[2-cyclopropyl-4-(4-fluorophenyl)quinoline-3-yl]-3,5-di- hydroxy-6-heptenoate by means of liquid chromatography using a packing material comprising a carrier and, carried thereon, a polysaccharide derivative, wherein a part or all of the hydrogen atoms of hydroxyl and amino groups of the polysaccharide derivative are substituted with one or more substituents, such as a carbamoyl group wherein one hydrogen atom is substituted with an aromatic group having a specific alkyl group. The method allows the production of the above (3R,5S,6E) isomer with enhanced productivity to a conventional method.