An AGC apparatus and method in a BWA communication system are provided, in which a MAP interpreter detects a beamformed symbol period in an (n−1)th signal, a symbol power calculator measures an average signal level of a symbol in an nth signal, and a beamforming gain calculator calculates a beamforming gain of the nth signal by adding a beamforming gain of the (n−1)th signal to a power difference between a signal of a beamformed symbol period and a signal of a non-beamformed symbol period in the nth signal using information about the beamformed symbol period of the (n−1)th signal and the average signal level of the symbol in the nth signal.