An automatic answering device and an automatic answering method for automatically answering to a user utterance are configured: to prepare a conversation scenario that is a set of input sentences and replay sentences, the input sentences each corresponding to a user utterance assumed to be uttered by a user, the reply sentences each being an automatic reply to the inputted sentence; to accept a user utterance; to determine the reply sentence to the accepted user utterance on the basis of the conversation scenario; and to present the determined reply sentence to the user. Data of the conversation scenario have a data structure that enables the inputted sentences and the reply sentences to be expressed in a state transition diagram in which each of the inputted sentences is defined as a morphism and the reply sentence corresponding to the inputted sentence is defined as an object.