An object is to provide: novel quinolinone glycosides which are useful as medicines; processes for producing the quinolinone glycosides; intermediates for synthesis; and medicines, and particularly anti-allergic agents, which comprise the quinolinone glycoside as an active ingredient. The object is achieved by: a quinolinone glycoside or a physiologically acceptable salt thereof; processes for producing this quinolinone glycosides; intermediates for synthesis; and medicines, and particularly anti-allergic agents, which comprise the quinolinone glycoside as an active ingredient; the quinolinone glycoside being expressed by general formula (I): (wherein, in the formula, each of R1 and R2 is a hydrogen atom or a glycosyl group selected from the group consisting of a glucuronyl group, a glucosyl group, a galactosyl group and a mannosyl group, and at least one of R1 and R2 is a glycosyl group in which a hydroxyl group in the glycosyl group is unprotected or protected with an acyl group having a carbon number of 2 to 7 or a benzyl group).