Operations are appropriately changed in accordance with the use method. A keyword detection unit 11 generates a keyword detection result indicating a result of detecting an utterance of a predetermined keyword from an input voice. A voice detection unit 12 generates a voice section detection result indicating a result of detecting a voice section from the input voice. A sequential utterance detection unit 13 generates a sequential utterance detection result indicating that a sequential utterance has been made if the keyword detection result indicates that the keyword has been detected and if the voice section detection result indicates that the voice section has been detected.