An apparatus and method are capable of controlling the output of the system utterance upon the occurrence of barge-in utterance and enabling a smooth interactive between a user and the system. Fade processing is applied to lower at least one of volume, a speech rate, or a pitch (voice pitch) of system utterance from a starting time of the barge-in utterance acting as the user interruption utterance during executing the system utterance. Even after the completion of the fade processing, the output state upon completing the fade processing is maintained. In a case where the system utterance level is equal to or less than the predefined threshold during the fade processing, the system utterance is displayed on a display unit. One of stop, continuation, and rephrasing is executed based on an intention of the barge-in utterance and whether an important word is included in in the system utterance.