It stores historical materials that are over a thousand years old from the "Mido Kanpakuki," diary by FUJIWARA no Michinaga (966 - 1028) in his own handwriting, an ancestor of the Konoe family, to the documents related to Fumimaro KONOE in the twentieth century, and it not only lets researchers read them but also publishes facsimile editions of them.
近衛家の遠祖にあたる藤原道長（966-1028）の自筆日記『御堂関白記』から、20世紀の近衛文麿の関係資料まで、1,000年以上にわたる歴史資料を収蔵し、研究者に閲覧の便を図るとともに、影印本の刊行などの事業を行っている。