The recovery of lithium ions by electrolysis using lithium ion conductive perovskite-type oxides La(2/3 - x)Li(3x)square(1/3 -2x)TiO(3), as a separator, has been carried out. It was confirmed that La(2/3 - x)Li(3x)square(1/3 - 2x)TiO(3) has the selective permeability for lithium ions, and La(2/3 -x)Li(3x)square(1/3 - 2x)TiO(3) can be applied to the electrochemical recovery for Lithium ions. Moreover, Li-6 ion was recovered in preference to Li-7 ion by this electrolysis. This indicates the possibility of isotope separation for the lithium, Li-6 and Li-7.