An anode active material for a lithium secondary battery includes a silicon alloy that includes silicon and at least one kind of metal other than silicon, the silicon alloy allowing alloying with lithium. A volume of an inactive region in the silicon alloy, which is not reacted with lithium, is 50 to 75% of the entire volume of an active material. The anode active material has a large capacity in comparison to carbon-based anode active materials, and also ensures small volume expansion and high capacity retention ratio after charging/discharging, resulting in excellent cycle characteristics.