A method for allocating resource to ACK (Acknowledgment)/NACK (Negative-ACK) transmission in a wireless communication system is disclosed. The method includes receiving scheduling information included in a plurality of downlink control channels and data included in a plurality of downlink data channels, over multiple downlink component carriers from a base station, determining ACK/NACK responses corresponding to the data, and allocating resource to the ACK/NACK responses based on the scheduling information corresponding to each of the plurality of downlink control channels and downlink component carrier-dependent offset values.