A method by which a small base station (BS) transmits a discovery signal (DS) in a mobile communication system is provided. The method includes a macro BS to which a component carrier (CC) of a predetermined frequency band is allocated, and at least one small base station to which N number of CCs of a frequency band different from that of the CC allocated to the macro base station are allocated. The method comprises the steps of generating the DS corresponding to predetermined information and transmitting the generated DS through a discovery channel (DCH) configured as a transmission resource of the macro base station, wherein the predetermined information is one among information on at least one CC that the small base station uses, cell ID (CID) index information of the small base station, and a sleep base station index when the small base station is in a sleep mode.