PURPOSE: To obtain an eye drop composition significantly low in eye irritancy containing, as medicinal ingredient, norfloxacin.

CONSTITUTION: This eye drop composition contains, as medicinal ingredient, 0.1-1wt.% of norfloxacin, 0.1-5wt.% of boric acid as an acidic substance, and, as the essential acidic ingredient, at least one kind of compound sea-ected from hydrochloric acid, citric acid, potassium dihydrogenphosphate and L-glutamic acid. This composition contains, other than the above ingredients, preservative, isotonicizing agent, dissolution auxiliary, thickening agent, chelating agent, etc., according as needed. It is preferable that this composition be prepared by first dissolving in water the boric acid and such amounts of the other acidic substance(s) as to be 4-6 in the pH level of the final composition and then dissolving the norfloxacin and the other ingredients in the water. Adjustment of the pH level of the composition using at least two kinds of the acidic substances including boric acid gives the objective eye drop significantly low in eye irritancy with the norfloxacin dissolved homogeneously without developing precipitation.