The present invention provides a lithium secondary battery having reduced internal resistance. The lithium secondary battery comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode comprises, as a positive electrode active material 30, a lithium transition metal composite oxide having a layered structure. In a surface region 82A of a positive electrode active material particle 82, at least one species among elements belonging to groups 3 to 7 of the periodic table is supplemented by ion implantation.