1. An ultrasonograph comprising a controller to which a probe and a display are connected, wherein: based on an analysis on a detected image of a target object detected by the probe, the controller generates a positional relationship image showing a positional relationship between the probe and the target object, and causes the display to display the positional relationship image; the positional relationship image is displayed on a part of the detected image; and a center line of the target object and a probe symbol indicative of a positional state of the probe including obliqueness of the probe with respect to the center line are displayed in the positional relationship image.