To reduce probability of a call setting failure in inter-network communication by means of setting re-call in a different route in spite of the call setting failure owing to a fault or the like at the side of another network by re-transmitting a call setting message by means of the route by way of a switch except the one for the transmission of a call release message.

When fault occurs between the switches 4 and 6 and the switch 4 detects that a route possible arrive to an incoming terminal does not exist, the call release message (b) is transmitted to the switch 2. When the setting of a specified disconnection reason is recognized in the call release message (b) which is received from the switch 4, the switch 2 edits information of the call release message (b) so as to permit the call to be the one blocked before passing a link with another network in appearance and transmits it to the switch 1. The switch 1 refers to information of the call release message (b), regards it an fault in the link of the switches 2-4 in a self network and executes the re-routing of the route to an incoming terminal 8 without passing through the link of the switches 2-4.