1. A knowledge extracting apparatus for extracting knowledge information from an electronic document, comprising: an information receiving section for receiving the electronic document; a knowledge extracting section for extracting a concept from the electronic document based on a target word to extract the knowledge information and a clue word to extract the knowledge information and forming knowledge information in which the concept thus extracted and the target word are associated with each other; a storage section for storing the knowledge information thus extracted; and an information analysis section for, after the knowledge information is stored, analyzing the electronic document based on the knowledge information stored in the storage section.