An image processor includes a signal processing circuit for performing signal processing on three-dimensional echo signals transmitted from an ultrasonic 3D probe, a memory for storing at least one set of plural sets of three-dimensional echo data converted by the signal processing circuit, a large capacity storage unit, a control circuit for controlling input/output signals from an input unit, an image processing circuit for performing image processing such as coordinate conversion based on the three-dimensional echo data stored in the memory, a display circuit for displaying the ultrasonic three-dimensional image processed by the image processing circuit, and a CPU for performing calculation for “volume measurement”. Accordingly, a tissue of interest can be easily and accurately measured.
