To provide a communication network system and a verification method capable of concentratedly verifying the communication state of the network system and easily segmenting a relay path where a fault is generated as well.

Respective nodes 10-1-10-5 for constituting this communication network system are provided with communication test data generation and transmission parts 15 and 16 generating and transmitting communication test date for communication verification and communication test data reception parts 14 and 17 for receiving the communication test data transmitted from the communication test data generation and transmission parts 15 and 16 of the other nodes respectively. The communication between the respective nodes is verified depending on whether or not the test data are normally transmitted between the respective nodes 10-1-10-5.