A radio communication method according to the present invention supports Dual registration in which the same UE (50) is simultaneously registered on 4G and 5G. The radio communication method includes the UE (50) requesting connection to EPC and transmitting, to the 4G, Attach Request that includes Dual registration indication that indicates that the UE (50) has been dually registered, and MME (100) that constitutes the 4G notifying, after the Attach Request has been acquired, HSS (110) of the Dual registration indication that indicates that the UE (50) has been dually registered.