A process for producing a lithium secondary battery employs a charging method where a positive electrode upon charging has a maximum achieved potential of 4.3 V (vs. Li/Li+) or lower. The process includes charging the lithium secondary battery to reach at least a region with relatively flat fluctuation of potential appearing in a positive electrode potential region exceeding 4.3 V (vs. Li/Li+) and 4.8V (vs. Li/Li+) or lower. The lithium secondary battery includes an active material having a solid solution of a lithium transition metal composite oxide having an α-NaFeO2 type crystal structure. The composition ratio of Li, Co, Ni, and Mn contained in the solid solution satisfies Li1+1/3xCo1−x−yNiy/2Mn2x/3+y/2(x+y≦1, 0≦y and 1−x−y=z).