In a network synchronization system including plural information processing devices, a first information processing device includes a synchronization-use common storage unit configured to copy and store first information for each user authorized to use the first information processing device, so that the first information can be shared with another information processing device; and a second information processing device includes a setting information unit configured to store second information for each user authorized to use the second information processing device, and a synchronization control unit configured to compare the second information with the first information, and to update the second information to latest information based on a result of the comparison. The synchronization control unit acquires common update information common to the information processing devices, which is stored in the synchronization-use common storage unit.