1. A question answering document retrieval system which executes document retrieval in accordance with a retrieval request in question form, comprising: retrieval means for retrieving associated documents on the basis of a keyword extracted from a question serving as a retrieval request in question form from a user, the retrieval means extracting descriptions associated with the keyword and contained in the retrieved documents as first summaries, thereby acquiring document retrieval results including a list of the extracted first summaries; question type determination means for determining a question type of the question by analyzing a semantic role of the question; summary extraction means for extracting descriptions corresponding to answers matching the determined question type as second summaries from original-document data which forms documents indicated by the document retrieval results, the original-document data being included in original-document data stored in an original-document database and forming each document as a retrieval target, the summary extraction means acquiring a list of the extracted second summaries; and an interface configured to display the document retrieval results and the list of the second summaries, as answers to the retrieval request from the user, on a display device which can be used by the user, the document retrieval results including the list of the first summaries.