An imaging device sets a first area and a second area other than the first area on a captured image; sets a main subject based on the captured image or another image; periodically detects the position of the main subject on the captured image; and performs control depending on a detection result so that it is indicated that the main subject exists only in the first area when the main subject does not exist in the second area, and it is indicated that the main subject does not exist only in the first area when the main subject exists in the second area.