NOVELTY - A lithium ion secondary battery has negative electrode having negative electrode active material layer containing negative electrode active material and negative electrode binder, positive electrode having positive electrode active material layer containing positive electrode active material and positive electrode binder, electrolyte solution and separator. Negative electrode binder is polymer obtained by polymerizing a monomer composition containing styrene monomer and ethylenic unsaturated-carboxylic-acid monomer.    USE - Lithium ion secondary battery is used as power supply for mobile telephone, notebook-type personal computer and electric vehicle.    ADVANTAGE - The lithium ion secondary battery has high capacity, charging/discharging characteristics, and safety.    DETAILED DESCRIPTION - A lithium ion secondary battery has a negative electrode having negative electrode active material layer containing negative electrode active material and negative electrode binder, a positive electrode having positive electrode active material layer containing positive electrode active material and positive electrode binder, an electrolyte solution and a separator. The negative electrode active material consists of carbonaceous active material. The negative electrode binder is polymer which is obtained by polymerizing the monomer composition containing (in parts mass) styrene monomer (70-90) and ethylenic unsaturated-carboxylic-acid monomer (1-5). The content of negative electrode binder with respect to 100 parts mass of negative electrode active material, is 0.1-5 parts mass. The positive electrode active material contains transition metal element(s) chosen from manganese, iron and nickel. The content of positive electrode binder with respect to 100 parts mass of positive electrode active material is 0.1-5 parts mass. The positive electrode binder is a polymer formed by polymerizing the monomer composition containing acrylonitrile monomer (10-35) and ethylenic unsaturated-carboxylic-acid monomer (1-10). The degree of swelling of positive electrode binder is 2-15 times.