A method of reusing a rechargeable battery includes collecting from users assembled batteries formed by rechargeable batteries, each holding initial individual information including at least a manufacturing date and an initial weight of the rechargeable battery. The collected assembled batteries are dismantled into rechargeable batteries, each holding the individual information. The rechargeable batteries of the dismantled assembled batteries are classified into groups based on the initial individual information of the rechargeable batteries and individual information of the plurality of rechargeable batteries obtained after the dismantling. A regenerated assembled battery is rebuilt reusing rechargeable batteries that have been classified into the same group.