A method for reusing a secondary battery by reusing unit cells or battery modules constituting reclaimed assembled batteries (or battery packs) to reconstruct a new assembled battery is disclosed. Assembled batteries are reclaimed, and disassembled into battery modules. The battery modules are selected based on battery characteristics such as an open-circuit voltage (OCV) and the like using an absolute acceptable range and a relative acceptable range, and a new assembled battery is rebuilt. The relative acceptable range is an acceptable range which is set for each assembled battery, and is set to have its center at an average value of a battery characteristic distribution.