An apparatus and method for beamforming in a broadband wireless communication are provided. The apparatus includes a first calculator for determining a degradation factor to indicate a degradation degree of a target signal due to interference cancellation by using a target channel matrix and at least one interfering channel matrix, a second calculator for determining a new noise power value to be used to calculate a beamforming vector if the degradation factor is greater than or equal to a threshold, and for determining the beamforming vector by using the new noise power value, and a beamformer for performing beamforming on a signal transmitted/received with a target Mobile Station (MS) by using the beamforming vector.