A speech dialogue system generates a response sentence in a way to improve the efficiency of the dialogue with the user, based on a result of estimation on an attribute of a proper name in an utterance of a user. The system includes a database attribute estimation unit to estimate the attribute of the input proper name by utilizing a database, and a web attribute estimation unit to estimate an attribute of an input proper name by utilizing information on the web. A reliability integration unit calculates integrated reliability of estimation for each of possible attributes obtained from the estimation by the units, by integrating first reliability of the estimation. A response generation unit generates a response sentence to an input utterance based on the integrated reliabilities of the possible attributes.