1. A question answering system comprising: a question input unit that receives an input question; a search unit that executes a first search processing on a basis of the input question; an answer candidate extraction unit that extracts an initial answer candidate on a basis of a result of the first search processing executed by the search unit; an answer candidate inspection unit that inspects the initial answer candidate extracted by the answer candidate extraction unit; and an answer output unit that outputs the initial answer candidate selected by the answer candidate inspection unit, as an answer of the input question, wherein: the answer candidate inspection unit generates one or more queries and executes a second search processing using the queries, each of the generated queries being a character string pattern relative to the input question and being generated based on one or more keywords included in the input question and one of the initial answer candidates extracted by the answer candidate extraction unit, the answer candidate inspection unit determines whether or not a composed word of a sentence, which is obtained as a result of the second search processing executed by the answer candidate inspection unit, has a similar lexical meaning to a lexical meaning of a specific word of the input question, and the answer candidate inspection unit selects the initial answer candidate included in the query, which is used when searching the sentence including the composed word that has the similar lexical meaning, as the answer.