An ultrasonic beam (40) for echo tracking is formed for a healthy portion (52a) of a bone (50) containing healthy portions (52a, 52b) and a fractured portion (54). Echo tracking processing is executed over the state where a load F is not applied to the bone (50) and the state where the load F is applied to the bone (50) so as to calculate a distortion amount of the bone (50) accompanying the load F via the ultrasonic beam (40) formed for the healthy portion (52a). The state of union of the fractured portion (54) is evaluated in accordance with the distortion amount obtained via the healthy portion (52a).
