In a reaction system having at least two liquid-liquid interfaces between an organic phase of raw material containing a compound(s) to be separated and an aqueous phase of an aqueous solution of inclusion-complexing agent and between that aqueous phase and an organic phase(s) of extraction solvent(s), the compound(s) to be separated is entrapped into the aqueous phase through formation of an inclusion complex(es) of the inclusion-complexing agent with the compound(s), while the compound(s) is entrapped into the organic phase(s) of extraction solvent(s) through dissociation of said inclusion complex(es). The foregoing operation is performed using, for example, a squarish U-shaped tube or an H-shaped tube with bottom plates. Preferred examples of inclusion-complexing agent include highly water-soluble branched cyclodextrins.