A mobile communication system includes a mobile station (5) connected to a core network (1) through a communication line intervened by a base station (3a), and a radio control station (2) configured for controlling the setting of a radio link for the mobile station (5) in the base station (3a). The base station (3a) monitors the congested state of the communication line, generates a state indicator indicating the congested state/non-congested state of the communication line, based on the results of monitoring, and transmits the state indicator generated to the radio control station (2). The radio control station (2) recognizes the current state of the communication line based on the state indicator received from the base station (3a).When the radio control station (2) recognizes that the communication line is in the congested state and receives a line connection request from the mobile station (5), the control station (2) transmits a control signal for refusing the line connection request received to the mobile station (5) without performing control for setting the radio link.