The invention provides a nonaqueous electrolyte secondary battery having a large battery capacity and excellent charge/discharge cycle characteristics. The nonaqueous electrolyte secondary battery includes a negative electrode including a particulate negative electrode active material (33), a positive electrode and a nonaqueous electrolyte. The particulate negative electrode active material (33) includes a plurality of two-phase regions (34) in the particle wherein the two-phase regions include a first phase (A) containing silicon and a second phase (B) containing silicon oxide disposed on the periphery of the first phase, the negative electrode active material being such that the ratio of the intensity at 480 cm−1 wavelength to the intensity at 510 cm−1 wavelength in a Raman spectrum obtained by Raman spectroscopy is not more than 0.1 and the ratio of the intensity at 2&thetas;=21.6 to the intensity at 2&thetas;=28.4 in an X-ray diffraction pattern obtained by X-ray diffractometry is not more than 0.1.