A question answering system includes a question dividing unit, a question answering unit, and an answer determination unit. The question dividing unit applies a predetermined question dividing rule to an input question, to divide the input question into sub-questions. The question answering unit acquires answer candidates corresponding to the sub-questions generated by the question dividing unit, together with certainty values serving as reliability indexes. The answer determination unit selects an answer to the input question from among the answer candidates acquired by the question answering unit.