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 from a user an input of a retrieval key used to search a search target document, the retrieval key to determine a display sequence of sentences extracted from the search target document in response to the search; an importance calculation hardware component for calculating an initial level of importance of each sentence included in the search target document, wherein the initial level of importance is determined by executing steps to: determine, for a first sentence in the search target document, a row vector having elements corresponding to each sentence in the search target document, wherein a first element of the row vector has a first position in the row vector corresponding to a position of a second sentence in the search target document and a value corresponding to a relevance between the first sentence and the second sentence, generate a matrix having rows corresponding to each sentence in the search target document, wherein a first row located at the first position amongst rows of the matrix is the first vector, and generate an eigenvector corresponding to a maximum eigenvalue of the matrix, wherein an initial level of importance of the first sentence is a value of a second element of the eigenvector located at the first position in the eigenvector; 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.