A radio base station device that is configured to relay a call connection of a radio terminal to a management device, comprising: a call connection control section for controlling the call connection of the radio terminal; and a position registration request section for requesting, of the management device, a position registration that associates identification information on the radio terminal with identification information on the radio base station device, wherein if the call connection control section receives (seq21, seq21_323) a handover request from the radio terminal that conducts the call connection through another radio base station device, then the call connection control section is configured to control the call connection of the radio terminal in such a manner that the radio base station device and the another radio base station device both relay the call connection of the radio terminal to the management device; and wherein while the radio base station device and the another radio base station device both relay the call connection of the radio terminal to the management device, the position registration request section is configured not to request the position registration of the management device, and if the call connection relayed, to the management device, by both the radio base station device and the another radio base station device is ended, then the position registration request section is configured to issue (seq50, seq51_323) a position registration deletion request to the another radio base station device and to request (seq54, seq55_323) the position registration of the management device in response to a received (seq53, seq54_323) position registration deletion reply from the another radio base station device. a call connection control section for controlling the call connection of the radio terminal; and a position registration request section for requesting, of the management device, a position registration that associates identification information on the radio terminal with identification information on the radio base station device, wherein if the call connection control section receives (seq21, seq21_323) a handover request from the radio terminal that conducts the call connection through another radio base station device, then the call connection control section is configured to control the call connection of the radio terminal in such a manner that the radio base station device and the another radio base station device both relay the call connection of the radio terminal to the management device; and wherein while the radio base station device and the another radio base station device both relay the call connection of the radio terminal to the management device, the position registration request section is configured not to request the position registration of the management device, and if the call connection relayed, to the management device, by both the radio base station device and the another radio base station device is ended, then the position registration request section is configured to issue (seq50, seq51_323) a position registration deletion request to the another radio base station device and to request (seq54, seq55_323) the position registration of the management device in response to a received (seq53, seq54_323) position registration deletion reply from the another radio base station device.