Disclosed is a negative active material for a rechargeable lithium battery comprising a Si phase, a SiM phase and at least one of a X phase and a SiX phase, wherein each of phases has a crystal grain size of 100 nm and 500 nm. The element M is at least one selected from the group consisting of Ni, Co, B, Cr, Cu, Fe, Mn, Ti, and Y, the element X is at least one selected from the group consisting of Ag, Cu, and Au. However, where M is Cu, X is not Cu.