As the Imperial Library was an institution that accepted books before the Second World War, its collection included all publications published in Japan after Meiji, and the collections of the two libraries became an important basis for NDL collection. Based on the model of the Library of Congress, this library was officially opened to ordinary readers on June 5th. 1948.

The Library of Parliament of Japan not only provides services for the Congress, but also undertakes the functions of the National Library. The library provides parliamentary meeting minutes, decrees, annual reports, pictures and historical records, as well as a picture database of precious cultural relics and modern books, which is rich in information.