Provided is an ultrasound imaging apparatus capable of reducing image artifacts generated during spatially encoded transmission/reception even when movement of the object being imaged occurs. To each of (at least two) transmitting aperture groups (110, 111) of an ultrasound probe (108) in order, a transmitting unit (102) causes the action of transmitting spatially encoded ultrasonic waves toward a prescribed location of an object that is being imaged (120) simultaneously from at least two transmitting apertures contained in the transmitting aperture group to be performed at least one time. A receiving unit (105) obtains a received signal by performing decoding and phasing of the output of a reception region (109). When doing so, the transmitting unit (102) inverts the spatially encoded code of the ultrasonic waves transmitted by some of the two or more transmitting aperture groups with respect to the spatially encoded code of the ultrasonic waves transmitted by the other transmitting aperture groups. An aperture synthesis unit (25) performs aperture synthesis of the reception signal obtained with the transmission of the transmitting aperture group (110) and the reception signal obtained with the transmission of the other transmitting aperture group (111).
