The present invention relates to wideband wireless access system, and more particularly to an effective method for transmitting control information during the combination of multiple carriers. As one embodiment of the present invention, there is provided a method by which a base station allocates a carrier to a terminal in a wideband wireless access system supporting multiple carriers, the method comprising: transmitting, to the terminal, a terminal specific or terminal group specific carrier allocation information that includes information about at least one of control information and data; and transmitting, to the terminal, a carrier combination control information that includes information about a change in the at least one candidate carrier available.