Separation of lithium isotopes was investigated by chemical ion exchange with a hydrous manganese(IV) oxide ion exchanger using an elution chromatography. The capacity of manganese(IV) oxide ion exchanger was 0.5 meq/g. One molar CH3COO Na solution was used as an eluent. The heavier isotope of lithium was enriched in the solution phase, while the lighter isotope was enriched in the ion exchanger phase. The separation factor was calculated according to the method of Glueckauf from the elution curve and isotopic assays. The single stage separation factor of lithium isotope pair fractionation was 1.021.