Key information that is currently in use is archived in a management server to prevent the key information from being lost. A storage device 10 is communicatably connected to a management server 60 managing key information 1. The storage device includes a memory device 21, and a controller 100 controlling the memory device. The controller implements encryption processing on data inputted and outputted to and from the memory device by using the key information. When stoppage of an operation is indicated, the controller determines whether the key information used by the controller is managed by the management server, stops the operation in a case where the key information is managed by the management server, and does not stop the operation in a case where the key information is determined not to be managed by the management server.