A resource allocation method and apparatus for an OFDMA-based mobile communication system that allows allocating resources of multiple carriers is provided. A Physical Downlink Control Channel (PDCCH) transmission method for allocating resources in multiple frequency bands of a mobile communication system based on an Orthogonal Frequency Division Multiple Access (OFDMA) according to the present invention includes generating and transmitting, at a base station, multiple PDCCHs for allocating resources in the multiple frequency bands using Control Channel Element (CCE) indices; and receiving and demodulating, at a user equipment, the multiple PDCCHs transmitted by the base station and locating the resources allocated in the multiple frequency bands using the CCE indices of respective PDCCHs. A Physical Downlink Control Channel (PDCCH) transmission apparatus for allocating resources in multiple frequency bands of a mobile communication system based on an Orthogonal Frequency Division Multiple Access (OFDMA) according to the present invention includes a base station apparatus which generates and transmits multiple PDCCHs for allocating resources in the multiple frequency bands using Control Channel Element (CCE) indices; and a user equipment which receives and demodulates the multiple PDCCHs transmitted by the base station and locates the resources allocated in the multiple frequency bands using the CCE indices of respective PDCCHs.