PURPOSE: To provide an isotope separating device, with which adhesion of neutral atoms to recovery electrodes can be prevented from occurring and the utilization efficiency of the raw material and the separation efficiency of the isotope can be improved.

CONSTITUTION: The recovery electrodes consist of the anodes 14 and the cathodes 15, both of which are arranged alternately one by one in the enclosure vessel 11 placed in the vacuum vessel 2. The region of the recovery electrodes is irradiated with the laser beam 12 to separate the ionized isotope 13. The evaporating crucible 4 contg. the raw metallic material 3 is provided in front of the anodes 14 and cathodes 15 and the vapor stream collecting plate 16 is provided at the back of them. This raw metallic material 3 is irradiated with the electron beam 7 to heat it and to convert it into the vapor stream 10. Each of the straightening plates 17 which are fitted with the respective rotating mechanisms 18, is provided one by one in the lower part of each of the anodes 14 and the cathodes 15. Since a large number of neutral atoms are present in the vessel 11 at the time of starting the operation, then the flow of the vapor stream 10 is restricted to prevent the adhesion of the neutral atoms to the recovery electrodes, namely to the anodes 14 and the cathodes 15 form occurring by using these straightening plates 17.