A lithium ion secondary battery includes a positive electrode including a positive electrode active material having a composition represented by the formula (1) LixNiyCozMtO2  (1) (wherein the element M is at least one kind selected from the group consisting of Mg, Ba, Al, Ti, Mn, V, Fe, Zr, and Mo and x, y, z, and t satisfy the following formulae: 0.9≦x≦1.2, 0≦y≦1.1, 0≦z≦1.1, and 0≦t≦1.1), and a negative electrode including a negative electrode active material mainly containing silicon and silicon oxide, and having an absorbance of 0.01 to 0.035 at 2110±10 cm−1 according to an FT-IR method.