Modified firmware is registered and controlled, and, when a download request is received from a terminal device, unupdated firmware is determined and downloaded to the terminal device. User identification information obtained from the download request is acquired, and, if the user identification information matches the user identification information of another terminal device that is already carrying out download, the download to the terminal device that output the download request is stopped. Even when the user identification information matches the user identification information of the other terminal device that is already carrying out download, if it is determined to be a download request by an operator operation, stopping the download is cancelled so as to execute the download, and a forcible termination notification is transmitted to the other terminal device that is already executing download so as to interrupt the download thereof in the process.