An information processing device performs software license authentication while sharing the license between an operational system and a standby system in a closed network. A license file and a license key are installed in the operational system. License synchronization starts between the operational system and the standby system. When the operational system fails, the operational system is separated from the closed network, and when a different device is provided, license synchronization is performed between the different device serving as a new standby system and a new operational system (old standby system). When the standby system fails, the standby system is separated from the closed network, and license synchronization is performed between a different device serving as a new standby system and the operational system. A device which retains the license monitors whether or not an unauthorized use of the license is conducted in the closed network.