A document retrieval system retrieving a document with the concept of the document taken into account is provided. The system includes a processing portion and the processing portion creates a retrieval graph from a retrieval composition. The retrieval graph includes first to m-th retrieval local graphs (m is an integer of greater than or equal to 1), and the retrieval local graphs are each constituted by two nodes and one edge. The processing portion performs retrieval of first to m-th sentences on a reference document. The i-th sentence (i is an integer of greater than or equal to 1 and less than or equal to m) includes one of the two nodes in the i-th retrieval local graph or a related term or a hyponym of the one of the two nodes; the other of the two nodes in the i-th retrieval local graph or a related term or a hyponym of the other of the two nodes; and the edge in the i-th retrieval local graph or a related term or a hyponym of the edge. A mark is assigned to the score of the reference document in accordance with the number of sentences included in the reference document among the first to m-th sentences.