1. An image observation apparatus comprising: an extraction unit configured to extract a plurality of medical images as a list display target from an image storage unit storing a plurality of medical images and an plurality of apparatus types in association with each other; a list generation unit configured to generate a list in which a plurality of reduced images respectively corresponding to the plurality of extracted medical images are arranged, the plurality of reduced images are arranged for each apparatus type in the list, and the list clearly indicates a reduced image corresponding to a candidate image of the plurality of extracted medical images that is more likely to be used; and a display configured to display the generated list.