Ultrasound imaging apparatus including a two-dimensional array of plural transducer elements distributed two-dimensionally and transmits and receives ultrasonic waves while scanning an area to be imaged to create an ultrasound three-dimensional image. Transducer elements are divided into plural element blocks including a first element block of which a size in a second direction of an arrangement surface of the two-dimensional array is larger than a size in a first direction of the surface, and a second element block of which a size in the first direction is larger than a size in the second direction. Each of the element blocks is divided into a predetermined number of groups to form a transmit beam and plural receive beams in the area to be imaged. Further included is a selecting means for making transmit/receive channels of the transducer elements grouped to be one channel in each of the groups.
