To provide a lithium secondary battery with excellent liquid leakage resistant property and high safety, restraining the heat generated before the current breaking function of a separator working even in an overcharged state, and breaking excessive charging current by making the current breaking function of the separator surely operate.

The lithium secondary battery comprises a positive electrode formed by arranging a positive electrode mixture layer containing positive electrode activator capable of doping/dedoping lithium ion on a positive electrode current collector, a negative electrode formed by arranging a negative electrode mixture layer containing negative electrode activator capable of doping/dedoping lithium ion on a negative electrode current collector, and a separator made of a microporous resin film interposed between the positive electrode and the negative electrode, and the surface of the negative electrode mixture layer is made to have a surface finish Rz (average roughness of ten points) of 2-8μm. It is recommendable to make the negative electrode mixture contain fibrous carbon by 0.5-5 mass%.