A lithium secondary battery comprises a negative electrode containing lithium metal or a material previously storing lithium as an active material, a positive electrode containing a positive active material, and an electrolyte containing a non-aqueous electrolyte solution. The positive active material is a thin film formed by depositing on a substrate from vapor phase or liquid phase and including an oxide containing at least iron as a main constituent by a sputtering method, a reactive deposition method, a vacuum deposition method, a chemical vapor deposition method, a spraying method, a plating method, or a method in combination of these methods.