A molten salt electrolysis apparatus and a molten metal electrolyzing method using such a device are disclosed having an electrolysis vessel (4) accommodating melt electrolyte including melt metal chloride, and an electrode unit (1) having electrically conductive electrodes (8), first insulation members (9) covering upper end surfaces of the electrodes and fixed thereto while extending upward from the upper end surfaces, second insulation members (10) covering lower end surfaces of the electrodes and fixed thereto while extending downward from the lower end surfaces, and an electrode frame (12) composed of an insulating body surrounding the electrodes, the electrode unit being immersed in the melt electrolyte.