The inventory processing unit reads by the barcode reader barcode labels of medium cartridges by scanning a plurality of times per one label as the carrier robot is moved in a predetermined cell array direction in the medium storage and notifies of stored medium information the high-order device. The cause of error specification processing unit extracts the error data from the scanning data obtained at the completion of the inventory process to determine the presence or absence of a barcode label and if it is determined that a barcode label exists, the predetermined retry process is executed, otherwise, notifies of the determination result the high-order device without executing the retry process.