Provided is a sodium secondary battery capable of operating at a low temperature. More particularly, the sodium secondary battery according to the present invention includes: an anode containing sodium; a cathode containing a transition metal and an alkali metal halide; and a sodium ion conductive solid electrolyte provided between the anode and the cathode, wherein the cathode is impregnated in a molten salt electrolyte containing a sodium.metal halogen salt including at least two kinds of halogens.