A molten salt electrolysis tank, comprises: an anode feeder which is equipped with a mechanism for recovering deteriorated contact resistance that takes place between the metal fuel rod and the anode in the course of the anodic electrolysis; a cathode feeder which is controlled so as to have a potential in a range that causes U and/or Pu ions to be reduced to metal; a heating mechanism for locally heating the metal fuel rod and/or an excitation mechanism for bringing the metal fuel rod into a locally excited state; and a solenoid coil or a permanent magnet that is disposed between the anode feeder and the cathode feeder so as to improve separation efficiency of U and/or Pu ions by applying a combination of an electric field and a magnetic field.