The present invention relates to a method and to an apparatus for allocating a bandwidth in a wideband wireless communication system. Said method comprises: allocating a bandwidth to an uplink burst area in accordance with the bandwidth request received from at least one terminal; determining whether a preemptive grant bandwidth allocation is enabled or not; determining a preemptive grant terminal if the preemptive grant bandwidth allocation is enabled; and allocating a preemptive grant bandwidth within a residual bandwidth to the determined preemptive grant terminal. By doing this, the present invention can efficiently use the bandwidth of an uplink frame, and shorten the time taken for bandwidth request/approval between a terminal and a base station.