A transmission/reception unit transmits an ultrasonic wave to a subject via the ultrasonic probe, receives an ultrasonic wave reflected by the subject, and outputs an echo signal corresponding to the received ultrasonic wave. A first volume data generating unit generates first volume data based on the echo signal. A second volume data generating unit generates second volume data by applying, to each voxel contained in the first volume data, three-dimensional filtering with a filtering characteristic corresponding to three-dimensional directivity of the voxel. An image data generating unit generates data of a two-dimensional ultrasonic image based on the second volume data.
