In performing aperture synthesis according to an ultrasound imaging apparatus, the amount of spatial change of amplification factors of phasing signals at respective receive phasing points are reduced, and a high-quality image is obtained. In a receive beamformer that generates an inter-transmission weight in accordance with a phasing range, and performs aperture synthesis processing, the inter-transmission weight being generated is applied to the receive phasing points within the phasing range obtained through transmission and reception, and the inter-transmission synthesis is performed. The inter-transmission weight is generated in such a manner that a variation form of the amplification factor between adjacent receive phasing points is smoothed and a difference of the amplification factor is reduced, as to each receive phasing point after the inter-transmission synthesis is performed.
