1. An apparatus for retrieving and outputting a specific sentence included in a document, the apparatus comprising: a retrieval key acquiring hardware component for acquiring a retrieval key used to search a search target document; an importance calculation hardware component for calculating an initial level of importance of each sentence included in the search target document; an extraction hardware component for searching the search target document using the retrieval key acquired by the retrieval key acquiring hardware component to extract a sentence including the retrieval key from the search target document in order to acquire position information on the extracted sentence in the document; an importance correction hardware component for correcting a value of importance of each sentence calculated by the importance calculation hardware component for the sentence extracted by the extraction hardware component based on the position of the sentence in the search target document obtained by the extraction hardware component to calculate a corrected level of importance; and a retrieval result outputting hardware component for outputting the sentence extracted by the extraction hardware component according to an order based on the corrected level of importance calculated by the importance correction hardware component.