A battery with a high capacity and superior cycle characteristics and an anthode active material used in the battery are provided. An anode includes an anthode active material capable of reacting with lithium. The anthode active material includes tin, cobalt and carbon as elements, and the carbon content is within a range from 9.9 wt % to 29.7 wt % inclusive, and the ratio of cobalt to the total of tin and cobalt is within a range from 30 wt % to 70 wt % inclusive. Moreover, the size of a crystalline phase of an intermetallic compound of cobalt and tin measured by small-angle X-ray scattering is 10 nm or less. Thereby, while a high capacity is maintained, cycle characteristics can be improved.