In a time synchronization system between wireless nodes, a first wireless node broadcasts a neighbor search packet, adjacent wireless nodes receive the neighbor search packet and then returns an adjacent response packet, the first wireless node selects the mediating wireless node based on the adjacent response packet and then transmits a mediating request packet to the mediating wireless node, the mediating wireless node receives the mediating request packet and then broadcasts a time record request packet, the first wireless node receives the time record request packet and then records reception time, the adjacent wireless nodes receive the time record request packet and then records reception time, the higher-level adjacent wireless node transmits a time notification packet containing the reception time to the first wireless node, and the first wireless node calculates the difference between the recorded reception time and the reception time contained in the time notification packet and then adds the difference to current time.