Provided is a method of manufacturing a lithium secondary battery, the method including: preparing positive and negative metal foams having a plurality of first pores; controlling first pore sizes of the metal foams depending on an application; filling the first pores with a slurry obtained by mixing a positive electrode active material or a negative electrode active material, a binder, a conductive material, and an organic solvent; heat-treating the metal foams to form second pores having a size smaller than those of the first pores. The first pore size of the metal foam can be controlled, so that a high capacity and high output battery can be manufactured depending on the usage.