An ultrasound diagnostic device has a control unit (18) which sequentially selects transducers (2a) for supplying drive signals while shifting a predetermined number of the transducers in a disposing direction for each output of transmitted ultrasound waves. Then, an image generation unit (14) generates image data for within a subject body for each frame on the basis of received signals which have been sequentially received by a receiving unit (13). Next, the control unit (18) performs switching between selection of m units of transducers (2a) to be consecutively positioned, and selection of m+1 units of the transducers (2a) to be consecutively positioned, for each frame. In addition, the control unit (18) generates synthesized image data acquired by synthesizing image data of at least two consecutive frames each time that image data is generated for each frame.