A network synchronization method allows reduced frequency fluctuations due to synchronization control in a network. Each node connected to the network has time information individually varying in a period of T. A time master node periodically notifies its own time information to time slave devices. Each time slave node prepares update-possible time points having a period of T/N (N > 1). When receiving master time information, each time slave node updates its own time information using the master time information at an update-possible time point just after the master time information has been received. |