The present invention aims to provide a technique enabling an information added by another user to be referenced and enabling the range of the information the user references from a database to be customized. A related information database in which a plurality of elements are accumulated is prepared, and an output setting information in which an information relating to the output of an additional information is associated with each other, in response to the additional writing of the additional information by a certain user to the related information database is stored. The output setting information of the certain user can be changed by the user. A portion of information is extracted from the related information database in accordance with an input of an extraction condition by the user, and the portion of information is visually output according to information relating to the output of the user.