PURPOSE: To separate effectively multi-valence metals from a solution liquid by touching an ion exchanger which contains at least one phosphorus atom in the ion exchanging radical, to a solution liquid which contains metallic ions.

CONSTITUTION: An ion exchanger containing at least one phosphorus atom in the ion exchanging radical can be shown as a constitutional formual, R-P (O)(OH)2, for instance. In the formula, the R stands for a radical body of the the ion exchanger and the -P(O)(OH)2 stands for an ion exchange radial. The OH polarizes into such as O-H+ and the H+ ion-exchanges with dissolved metal lic ions to capture the metallic ions in the ion exchanger. An ion exchanger 1 having such a characteristic, and an object solution liquid 2 containing multi- valence metallic ions are injected into a separation vessel 4 and is left for a certain time period and therewith, since the object metallic ions are cuptured by the ion exchanger 1 and settles down gradually to a bottom part of the vessel 4, the treated solution liquid is taken out of the vessel after settling. In such a way, processing of radioactive waste, and the like, can be conducted very easily since the object metals can be separated from the solution liquid by a simple operation.