A control message transmitting/receiving method in an MBMS-supporting mobile communication system. In the present invention, an RNC periodically transmits control messages related to MBMS RB setup to UEs. Thus, although a UE initially fails to receive an intended MBMS service, it can set up an MBMS RB by receiving a related retransmitted control message. Also, the RNC periodically provides information about ongoing MBMS services on a cell basis so that a UE can decide whether its requested MBMS service is in progress and request information required to set up an MBMS RB for the MBMS service to the RNC by individual signaling.