PURPOSE: To carry out efficient isolation of abscisic acid in high selectivity and yield from a dilute solution of abscisic acid without concentration of the organic layer extracting abscisic acid using a reduced amount of the solvent.

CONSTITUTION: The isolation process for abscisic acid comprises the extraction step of bringing the aqueous abscisic acid into contact with an organic solvent immiscible with water to transfer the abscisic acid into the organic solvent, the adsorption step of bringing the organic layer containing abscisic acid into contact with an adsorbent to transfer the abscisic acid into the adsorbent, the recycling step of recycling the organic layer from which abscisic acid is desorbed to the extraction step, and the isolation step of isolating abscisic acid from the solution separated. The isolated abscisic acid lower the purification load thereafter to give ABA of high purity inexpensively in an industrial scale.