To provide a means capable of improving the cycle durability of an electric device such as a lithium ion secondary battery. A negative electrode active material containing a silicon-containing alloy having ternary alloy composition represented by Si—Sn-M (M is one or two or more transition metal elements) or quaternary alloy composition represented by Si—Sn-M-Al (M is one or two or more transition metal elements) and having a structure wherein an a-Si phase containing amorphous or low crystalline silicon containing tin in a silicon crystal structure in form of a solid solution is dispersed in a silicide phase containing a silicide of a transition metal as a main component is used in an electric device. The negative electrode active material improves the cycle durability of an electric device such as a lithium ion secondary battery.