A reconstituted battery pack producing method comprises an obtaining process for obtaining, by use of one of a first charged-state control device having ever controlled a charged state of a used battery pack when it was used before and a second charged-state control device arranged to control the charged state of the used battery pack as with the first charged-state control device, a reference-time charge amount charged in each used secondary battery constituting the used battery pack; a selecting process for selecting more than one of the used secondary batteries close to each other in the reference-time charge amount from a group of the used secondary batteries whose reference-time charge amounts have been obtained; and an assembling process for combining and assembling the selected used secondary batteries into a new reconstituted battery pack.