A technique for displaying an ultrasonic three-dimensional image and its tomographic image at the same time is disclosed. According to the technique, it is provided with: a transmitting/receiving circuit 111 for carrying out a transmitting/receiving control of ultrasonic waves a three-dimensional processing unit 120 for forming a three-dimensional image from an ultrasonic reception signal received by the transmitting/receiving circuit an image processing circuit 115 for converting the tomographic image and the three-dimensional image into a display format and the like. The three-dimensional processing unit is composed of: an angle detecting circuit 121 for generating an angle information of a high resolution from two encoder signals of a rotation and an oscillation and a high speed operation processing circuit 122 for carrying out processes of generation, treatment and cut of a three-dimensional image data, and the like.
