In cycles of charging and discharging, an excellent capacity maintenance rate is obtained. The charging and discharging cycle characteristic of battery is enhanced. Further, an excellent initial discharging capacity is obtained. A negative electrode, a positive electrode, and a non-aqueous electrolyte are contained. The negative electrode includes an alloy of Si, a first element and a second element. The first element includes at least one element selected from the group consisting of the second group element except Mg in the periodic table, transition elements, twelfth group element, thirteenth group element except B, and fourteenth group element except Si. The second element includes at least one element of B and Mg.