A mobile communication system comprising: first and second base stations (1-1, 1-2) located in a radio access network and configured to be connected to a core network; a relay station located in the radio access network and configured to belong to any one of the first and second base stations (1-1, 1-2) and perform radio relay between a mobile station and the first or second base station; first data transfer means located in the core network and configured to terminate a mobile-station data bearer provided between the mobile station and the first data transfer means through the relay station, and transfer user data to the mobile station using the mobile-station data bearer; second data transfer means with the functions of a serving gateway and packet data network gateway for the relay station located in the first base station and configured to terminate a relay-station data bearer provided between the relay station and the second data transfer means, and transfer the user data between the first data transfer means and the relay station by associating the mobile-station data bearer with the relay-station data bearer; third data transfer means located in the second base station and configured to terminate the relay-station data bearer, and relay-station mobility management means configured to, when a belonging destination of the relay station is changed from the first base station to the second base station, change (S109, S111) a path of the relay-station data bearer, which is terminated by the relay station and the second data transfer means, so as to pass through the second base station wherein the second data transfer means is a mobility anchor point and there is no change of the second data transfer means terminating the relay-station data bearer, wherein the system is characterised in that the relay-station mobility management means is configured to, after changing the path of the relay-station data bearer accompanying the change of the belonging destination of the relay station, modify a termination point of the relay-station data bearer from the second data transfer means to the third data transfer means in response to a predetermined condition being satisfied. first and second base stations (1-1, 1-2) located in a radio access network and configured to be connected to a core network; a relay station located in the radio access network and configured to belong to any one of the first and second base stations (1-1, 1-2) and perform radio relay between a mobile station and the first or second base station; first data transfer means located in the core network and configured to terminate a mobile-station data bearer provided between the mobile station and the first data transfer means through the relay station, and transfer user data to the mobile station using the mobile-station data bearer; second data transfer means with the functions of a serving gateway and packet data network gateway for the relay station located in the first base station and configured to terminate a relay-station data bearer provided between the relay station and the second data transfer means, and transfer the user data between the first data transfer means and the relay station by associating the mobile-station data bearer with the relay-station data bearer; third data transfer means located in the second base station and configured to terminate the relay-station data bearer, and relay-station mobility management means configured to, when a belonging destination of the relay station is changed from the first base station to the second base station, change (S109, S111) a path of the relay-station data bearer, which is terminated by the relay station and the second data transfer means, so as to pass through the second base station wherein the second data transfer means is a mobility anchor point and there is no change of the second data transfer means terminating the relay-station data bearer, wherein the system is characterised in that the relay-station mobility management means is configured to, after changing the path of the relay-station data bearer accompanying the change of the belonging destination of the relay station, modify a termination point of the relay-station data bearer from the second data transfer means to the third data transfer means in response to a predetermined condition being satisfied.