To provide an emergency call service the same as in a home network by permitting a visitor network exchange to convert an emergency call number which is the same as the emergency call number in the home network and dialed by an international roaming subscriber, into the emergency call number of a visitor network.

The B-side visitor network exchange 202 receives an authenticating information response signal from a B-side visitor location resistor(VLR). Then, the exchange 202 receives an authenticating response signal from a roaming machine 500 and transmits an emergency call information requesting signal to the B-side VLR 201 for originating an emergency call in the case of OK by an authentication check. The exchange 202 converts it into the emergency call number in the visitor network. A communication line for executing routing to an emergency call receiving stand storing exchange is picked-up and a call signal is transmitted. When the call signal is received from an incoming side exchange, the B-side visitor network exchange 202 transmits the call signal to the roaming machine 500 and the exchange 202 transmits a response signal to the machine 500.