A negative electrode active material which has a ternary alloy composition represented by Si—Sn-M (M is one or two or more transition metal elements) and has a microstructure which has a first phase (silicide phase) having a silicide of a transition metal as a main component and a second phase partially containing Sn and having amorphous or low crystalline silicon as a main component, and further has partially a plurality of independent first phases and partially a eutectic structure of the first phase and the second phase is used for an electric device. The negative electrode active material improves cycle durability of an electric device such as a lithium ion secondary battery.