An information processing device of the present invention includes a sightline distance calculating unit (106) configured to calculate a sightline distance between a position of a user and a position of a point specified on an image display surface based on a sightline direction of the user, a character size calculating unit (108) configured to determine a character size in accordance with the sightline distance calculated by the sightline distance calculating unit (106), and a display control unit (110) configured to determine a size of a display image in accordance with the character size calculated by the character size calculating unit (108).