PURPOSE: To improve the sepn. efficiency of the specific isotope which is the object to be recovered by providing a thermal dissociation ion remover disposed with a meshed electrode to be impressed with a voltage below the respective electrodes of a product recovering electrode so as to intersect with the flow direction of vapor flow.

CONSTITUTION: A crucible 4 for evaporation in which a metallic raw material 3 is housed is disposed in a vacuum vessel 2 and the vapor flow 7 of the raw material 3 is generated by heat sources 5, 6. The product recovering electrode 10 consists of the positive electrodes and negative electrodes which are alternately juxtaposed and erected in the direction not intersecting with the flow direction of the vapor flow 7 and are impressed with the voltage above the crucible 4. A waste recovering plate 11 is disposed to cover the space above the electrode 10. The electrode 10 is irradiated with a laser beam 9 intersecting with the flow direction of the vapor flow 7 between both electrodes thereof. The thermal dissociation ion remover 12 disposed with the meshed electrode 14 to be impressed with the voltage is provided below the respective electrodes of the electrode 10. Consequently, the sepn. efficiency of the specific isotope is improved.