PROBLEM TO BE SOLVED: To determine accurately whether a question sentence is a question sentence in a specific field or not.SOLUTION: A question answering device 10 includes a question sentence input part 11 for inputting a question sentence, an entity extraction part 12 for extracting an entity which is a question object from an inputted question sentence, a perplexity calculation part 13 for calculating the value of perplexity based on a language model in which a question sentence in a specific field is assumed from the inputted question sentence, and a determination part 14 for determining whether the inputted question sentence is a question sentence in the specific field or not based on the extraction result of the entity and on the calculated perplexity value.
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