An object of the present invention is to provide efficient RFN timing passing between a User Plane Server (UPS) and Radio Control Server (RCS). In a radio base station control system that controls a radio base station device communicating with a mobile terminal over a radio link and includes an RCS performing signaling transfer control and a UPS performing user data transfer control relating to the terminal, the RCS and UPS being provided physically separated from each other, the RCS includes inquiry means for sending an inquiry signal for inquiring about timing information of the UPS, the timing information being required for signaling transfer control and being managed by the UPS; and the UPS includes sending means for sending the RFN to the RCS when the UPS receives the inquiry signal.