1. A region-of-interest extraction apparatus comprising: an acquisition unit configured to acquire a structured document and a plurality of display coordinates, the structured document including a plurality of first elements, the plurality of display coordinates indicating display positions of the a plurality of first elements when the structured document is displayed as an image; a first extraction unit configured to extract a plurality of block regions from the structured document, the plurality of block regions including a plurality of specific second elements of the plurality of first elements; a second extraction unit configured to specify one or more third elements displayed on a display screen based on plurality of display coordinates, and to extract, as a display region, displayed parts of the one or more third elements from the structured document; and a third extraction unit configured to extract, as a region of interest in which a user is interested, a block region from the plurality of block regions, the block region having an area in the display screen that is increased based on a difference between an area of the display screen from an extraction result obtained after scrolling and an area of the display screen from a previous extraction result based on an earlier time before scrolling and stored in a region-of-interest history storage.