A magnesium ion containing non-aqueous electrolyte in which magnesium ions and aluminum ions are dissolved in an organic etheric solvent, and which is formed by: adding metal magnesium, a halogenated hydrocarbon RX, an aluminum halide AlY3, and a quaternary ammonium salt R1R2R3R4N+Z− to an organic etheric solvent; and applying a heating treatment while stirring them (in the general formula RX representing the halogenated hydrocarbon, R is an alkyl group or an aryl group, X is chlorine, bromine, or iodine, in the general formula AlY3 representing the aluminum halide, Y is chlorine, bromine, or iodine, in the general formula R1R2R3R4N+Z− representing the quaternary ammonium salt, R1, R2, R3, and R4 represent each an alkyl group or an aryl group, and Z− represents chloride ion, bromide ion, iodide ion, acetate ion, perchlorate ion, tetrafluoro borate ion, hexafluoro phosphate ion, hexafluoro arsenate ion, perfluoroalkyl sulfonate ion, or perfluoroalkyl sulfonylimide ion.