To provide a non-aqueous electrolyte secondary battery which uses an active material employing magnesium as the base for a positive electrode and a negative electrode and has a high capacity, and is highly safe.

This is the non-aqueous electrolyte battery which comprises a non-aqueous electrolyte containing an ether series solvent containing an aliphatic ether and a magnesium salt such as bis(trifluoromethylsulfonyl)imide magnesium or trifluoromethyl-sulfonate magnesium, and a positive electrode and a negative electrode containing magnesium metal, magnesium alloy, magnesium oxide, silicon, carbon, carbon fluoride, and transition metal fluoride etc. as an active material.