DIALOGUE SYSTEM

Provided is a dialogue system where appropriate dialogue is conducted for a user when acquiring a question sentence in FAQ or the like. A key question sentence generation unit extracts one key from an answer database based on an initial key and generates a key question sentence. An output unit transmits an ask-back sentence including the key question sentence containing the one key and one or a plurality of initial keys to a user terminal. The output unit further transmits the initial key as an acquired key used for extracting the one key to the user terminal. By such processing, dialogue processing is performed by key input and an ask-back sentence in response to the key input.