A display controller includes a character display unit for displaying character information on a display unit; a keyword detecting unit for detecting a predetermined keyword from the character information displayed by the character display unit; an image information detecting unit for detecting image information including additional information corresponding to the keyword detected by the keyword detecting unit, from image information including predetermined additional information and stored in a storing unit; and a thumbnail image displaying unit for displaying on the display unit a thumbnail image(s) of the image information detected by the image information detecting unit.