PURPOSE: To provide an adsorptive separation method of a xylene isomer mixture by using carbon dioxide as a carrier and a desorbent.

CONSTITUTION: By introducing a certain amount of a xylene isomer mixture with a carrier of high pressure phase carbon dioxide into a bed of high silicon zeolite adsorbent, adsorption is performed and the first product flow including large amounts of metaxylene and orthoxylene is obtained after passing through the adsorbent bed. After a mixture of ethylbenzen and paraxylene appears in the flow, supercritical carbon dioxide under higher pressure is introduced to sorb the absorbent bed thereby obtaining the second product flow including large amounts of ethylbenzen and paraxylene. It is preferable to introduce each of the first product flow and the second product flow to different absorbent beds of active carbons, to adsorb those xylene isomers products under isothermal and isobaric conditions and to reuse while circulating substantially pure carbon dioxide passing through those adsorbent beds of active carbons.