A non-aqueous electrolyte secondary battery having a large capacity with improved charge/discharge characteristics is provided. The non-aqueous electrolyte secondary battery is fabricated by combining a positive electrode (4) and a negative electrode (2) so that the relationship: 0.9.ltoreq.Kp/Kn.ltoreq.1.1 is satisfied, where an initial efficiency of the positive electrode (4) is represented by Kp and an initial efficiency of the negative electrode (2) is represented by Kn. An active material of the positive electrode (4) preferably contains a lithium composite oxide having a composition of Li.sub.x Ni.sub.y M.sub.z O.sub.2 (0.8<.times.<1.5, 0.8