A bar is displayed in a second region. In an undetected state in which a region of interest is not detected, the length of the bar is 0, and when the undetected state transitions to a detected state in which the region of interest is detected, the bar increases in length over time. In addition, when the detected state transitions to the undetected state, display of the bar is continued with the length fixed. Thus, even in the undetected state, it is known that the region of interest has been previously detected. In addition, even in the undetected state, the region-of-interest detected duration is known from the length of the bar.