When a location-area MSC 20 receives an SMS originating signal, an
interrogating unit 21 sends an SRIforSM signal including the MSISDN of a
receiving terminal 10b to an HLR 30. When the location-area MSC 20
receives an SRIforSMack signal from the HLR 30, a
subscriber-identification-information obtaining unit 22 obtains an IMUI
contained in the SRIforSMack. An on-origination carrier identifying unit
23 identifies from the IMUI the carrier to which the receiving terminal
10b subscribes. The location-area MSC 20 determines whether the carriers
have an SMS interconnection agreement with each other, on the basis of
identification made by an on-origination carrier identifying unit 23.