The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and apparatus for allocating an uplink carrier for transmitting uplink control information in a wireless communication system that supports carrier aggregation. According to one embodiment of the present invention, a method for transmitting uplink control information in a wireless communication system that supports carrier aggregation of M (M≧1) uplink component carriers comprises: a step of receiving setup information on a primary uplink component carrier, from among said M uplink component carriers, via which one or more pieces of uplink control information are to be transmitted; a step of multiplexing said one or more pieces of uplink control information; and a step of transmitting the multiplexed uplink control information through the primary uplink component carrier.