To reduce cost by relieving an operation load by eliminating the necessity of changing processing of route information caused by VoIP of a telephone terminal, irrespective of the scale of a telephone exchange network.

Route information to a gateway server 3 independent from a telephone number is previously registered in each of relay exchanges 11 and subscriber exchanges 12. When an incoming call arrives, the relay exchange 11 or the subscriber exchange 12 which receives the incoming call accesses a VoIP terminal management server 23 managing an IP telephone terminal 21, and determines whether or not a telephone terminal 13 of a connection destination is managed as the IP telephone terminal 21. The route information corresponding to the telephone number or the route information to the gateway server 3 is selected on the basis of a result of the determination, and connection control is performed on the basis of the selected route information.