In message retrieval, a system is provided wherein both a message to be retrieved and a message related to the original message are acquired as a result of retrieval. The original message read from a DB 101 and displayed on a user's PC 108 by a message display section 103 is given to a response generating section 104. When a response message to the message is input by the user, and an instruction is given to the response generating section 104, a response message file is created, its file name is made by adding a branch number indicating the association to the file name of the original message file, and the response message file is stored in the DB 101 by a message storing section 102. When retrieving a message, a message file containing a keyword specified by the user is retrieved from the database by the message retrieving section 105 and, as a result of retrieval, the message file and a message file having a file name made by adding a branch number to the file name of the file are output.
