Ultrasonic images (302) are created by means of an ultrasonic probe (104). Volume image data (221) is created previously by using an image diagnosis apparatus (102) and stored in a volume data storage unit (107). From the stored volume image data (221), a tomogram corresponding to the scan surface of the ultrasonic images is extracted, and a reference image (301) is formed from the tomogram. A first reference point (223) is set on a distinctive point of the ultrasonic image (302) displayed on a displaying unit (114), a second reference point (222) is set on the distinctive point of the reference image (301) displayed on the displaying unit (114). A coordinate determining unit (109) determines a coordinate of the reference image (301) associated with the ultrasonic image (302) in accordance with the first reference point (223) and the second reference point (222). The reference image (301) is generated by associating a coordinate system of the volume image data (221) with a coordinate system of a scan plane of the ultrasonic image (302) based on the coordinate determined by the coordinate determining unit (109).
