The number of steps is reduced in the formation process of an electrode. Deterioration of the electrode is suppressed. A highly reliable lithium secondary battery is provided by suppressing the deterioration of the electrode. A method for forming a negative electrode and a method for manufacturing a lithium secondary battery including the negative electrode are provided. In the method for forming the negative electrode, graphene oxide, a plurality of particulate negative electrode active materials, and a precursor of polyimide are mixed to form slurry; the slurry is applied over a negative electrode current collector; and the slurry applied over the negative electrode current collector is heated at a temperature higher than or equal to 200° C. and lower than or equal to 400° C. so that the precursor of the polyimide is imidized. The graphene oxide is reduced in heating the slurry to imidize the precursor of the polyimide.