Time synchronization system, time master, management master and method for time synchronization

A time synchronization system of the present invention includes a plurality of time masters (2) and a management master (3). The management master (3) includes a management master priority request unit (32) which sends a priority request frame to each time master (2), and a management master highest priority processing unit (34) which sends a highest priority notification frame notifying changing the priority to the highest level to the time master (2) that holds the highest priority. The time master (2) include a time master priority response unit (22) which sends a priority response frame to the management master (3) after receiving the priority request frame therefrom, and a time master highest priority processing unit (24) which changes the priority to the highest level when receiving the highest priority notification frame from the management master (3). A grand master (1) sends to the remaining time masters (2) a time notification frame that synchronizes the time of the remaining time masters (2).