1. A dictionary creation device that creates a dictionary used for searching, classifying, or filtering information written as text, wherein keywords are registered in the dictionary per category, and wherein said dictionary creation device comprises: a classification information acquisition unit operable to acquire classification information regarding the category and text information from at least two information sources which differ from an information source of the information written as text; a keyword extraction unit operable to extract a keyword from the text information; a dictionary registration and deletion unit operable to register or delete the extracted keyword in dictionaries corresponding to the respective information sources, in accordance with the category, based upon the classification information acquired by said classification information acquisition unit and the keyword extracted by said keyword extraction unit; and a dictionary combining and editing unit operable to edit and combine the respective created dictionaries that correspond to each information source.