1. An ultrasonic diagnostic apparatus, characterized by comprising: means that acquires a three-dimensional ultrasonic signal of an internal organ of an examinee; means that sets a direction of a two-dimensional standard cross-section of the internal organ; means that adjusts display parameter of an image of a site which an examiner intends to observe; means that generates a two-dimensional standard cross-sectional image from the three-dimensional ultrasonic signal on the basis of the set direction of the two-dimensional standard cross-section of the internal organ; means that generates an observation cross-sectional image and a rendering image from the three-dimensional ultrasonic signal on the basis of the display parameters of the adjusted image; and display means that combines and displays the two-dimensional standard cross-sectional image, the observation cross-sectional image and the rendering image.