Provided is a battery pack producing method and a battery pack capable of suppressing defects such as overcharging or overdischarging in one or more of the used secondary batteries constituting a battery pack, and sufficiently exhibiting the performance of the used secondary batteries of the battery pack. This method includes an obtaining process for obtaining each full charge capacity of the used secondary batteries, a selecting process for selecting one or more used secondary batteries having similar full charge capacities from the used secondary batteries whose full charge capacities have been obtained, and an assembling process for assembling the selected secondary batteries.