A beamforming apparatus, an ultrasound imaging apparatus, and a beamforming method are disclosed. The beamforming apparatus according to an exemplary embodiment may include a filter to select predetermined first columns, which correspond to low-frequency components, among columns that composes a transform function； and a beamforming processor to transform an input signal to another space by using a transform function composed of the predetermined selected first columns, and generate a beam signal through signal processing in the transformed space.
