A processor of an endoscope system detects from the observation images a lesion area which is an observation target of the endoscope, judges a level of an oversight risk which is a risk that an operator may overlook the lesion area, on the basis of the observation images, and controls notification methods of detection of the lesion area on the basis of the level of the oversight risk. The processor displays the marker image indicating the lesion area only in a second image region of the display apparatus when a level of the oversight risk relating to the lesion area is a first level and displays the marker image in both a first image region and the second image region which is smaller than the first image region when a level of the oversight risk relating to the lesion area is a second level higher than the first level.