PURPOSE: To reduce the communication of the entire network and to recognize the operating state by setting an information circulation path to each information processing unit in the network, always monitoring the circulation destination and circulating the operating state information of all the information processing units.

CONSTITUTION: An operation start command form a monitor distribution means 15 is sent to all other information processing units by using a network transmission means 1. When a network reception means 2 receives the reply, the means 2 commands the operation start to a monitor control means 13. The means 13 reads the newest operating state information and uses the transmission means 1 to send a monitor packet to a monitor destination. The operating state information is revised by the monitor reply. Thus, the load of the monitor operation is decentralized to each information processing unit to decrease the traffic in the network and a fault takes place in the information a prescribed unit in monitor operation and even when the unit comes to a stop, the operating state monitor in the network is not stopped.