An object of the invention is to provide an ultrasonic diagnostic apparatus that can scan a region of interest at high speed and other regions at low speed.In the ultrasonic diagnostic apparatus of the invention, a two-dimensional array probe 1 formed by arranging a plurality of ultrasonic elements two-dimensionally transmits an ultrasonic beam to a three-dimensional region and receives a reflected signal. The ultrasonic beam scans a region on a pyramid, and the scan region is divided into a main scan region Am of a region of interest and a subscan region. The subscan region is divided into small regions As1, As2, As3, and As4. The number of main scanning times of the main scan region is larger than the number of subscanning times of the subscan region.
