A method and apparatus for providing an MBMS service to a plurality of cells in a mobile communication system are provided. In a mobile communication system including an RNC for providing an MBMS service and a plurality of Node Bs connected to the RNC, for providing the MBMS service to UEs within a plurality of cells. The RNC is configured to have a plurality of lower-layer entities corresponding to the cells. An RLC and PDCP entity that area common to the cells, receive MBMS data from an upper layer and transmit, upon receiving a request from one of the lower-layer entities, the MBMS data to the lower-layer entity. Therefore, the RNC can provide the MBMS service more efficiently, and unnecessary consumption of system resources is reduced.