PURPOSE: To efficiently and selectively isolate abscisic acid from a dilute solution containing the abscisic acid in high yield without concentrating an organic layer extracted with an organic solvent by reducing the amount of the organic solvent used.

CONSTITUTION: The method for isolating abscisic acid is characterized by comprising an extraction step for bringing an aqueous solution containing the abscisic acid into contact with an organic solvent immiscible with water and making the abscisic acid pass into the organic solvent, a back extraction step for bringing the organic layer, separated from the extraction step and containing the abscisic acid into contact with an aqueous solution of an alkali and making the abscisic acid pass into the aqueous solution of the alkali, a recycling step for recycling the organic layer subjected to the back extraction of the abscisic acid in the back extraction step to the extraction step and a step for isolating the abscisic acid from the aqueous solution of the alkali, separated in the back extraction step and containing the abscisic acid. The isolated abscisic acid is capable of reducing the subsequent purification load and providing an industrially inexpensive high-purity abscisic acid (ABA).