[Problems to be Solved] Facilitating the operation of aligning a scan plane by an ultrasonic probe with a cross-section that includes a puncture line. [Means for Solving the Problems] Scanning a subject with an ultrasonic probe and obtaining an ultrasonic image of the subject. Obtaining a cross-sectional image G2 of a cross-section of a three-dimensional image corresponding to the ultrasonic image G1 from the three-dimensional image, the three-dimensional image including a puncture line set for a puncture needle and a superimposed columnar index 45 having a central axis line on the puncture line and opacity which is reduced with the distance from the central axis line. Displaying the ultrasonic image G1 and the cross-sectional image G2. In this case, the thickness, opacity, and cross-sectional shape of the index 45 displayed on the cross-sectional image G2 vary according to the positional relationship between the scan plane of the ultrasonic probe and the cross-section in which the puncture line is set.
