In a mobile communication system, a handover of a terminal device (MT) from a macrocell base station (eNB) to a small cell base station (HeNB) is controlled via a host device (MME or HeNB-GW). Physical cell ID deployment map information (PCI deployment map information), which includes at least information (PCI/CGI map information) indicating the correspondences between physical cell IDs and unique cell IDs of CSG cells for which access is granted, is generated in the host device (MME or HeNB-GW). When the terminal device measures the reception quality for surrounding CSG cells for handover control to any of the CSG cells, the terminal device uses the PCI deployment map information to generate a measurement result report. Thus, a service interruption caused by handover control to an inaccessible small cell can be avoided, and the wait time for handover control can be reduced.