The National Diet Library got its start in the building that is now Japan's State Guest House. It opened there on June 5, 1948, using the former Akasaka Detached Palace as temporary quarters. The National Diet Library Law had been promulgated on February 9 of that same year, so the library opened less than four months after the law came into being.

An American mission and a debate in the Diet

An American mission had a hand in making that law. In December 1947, V. W. Clapp and C. H. Brown came to Japan as the United States Library Mission, at the request of the presiding officers of both houses of the Diet, Japan's parliament: the House of Representatives and the House of Councillors. The basic plan drawn up from their advice became the framework for the National Diet Library bill. The new library was modeled on the Library of Congress and took shape through debate in the Diet. The model lay across the ocean, but the books that would fill the new library were already in Japan.

Two roots and three buildings

The library has two roots. One is the pair of libraries that served the House of Peers and the House of Representatives of the Imperial Diet, Japan's prewar parliament, which opened in 1890. The other is the Imperial Library, founded under the Ministry of Education in 1872 as the Shojaku-kan. In 1947 the Imperial Library was renamed the National Library, and in 1949 it became the Ueno Branch Library of the National Diet Library. Nearly all the books from both libraries passed to the NDL.

The Imperial Library's building in Ueno is still in use. The brick building, put up for the Imperial Library in 1906, later served as the Ueno Branch Library and is now the International Library of Children's Literature, a specialist library for children's books from Japan and around the world. Part of it opened in May 2000, and it opened fully in May 2002.

The Tokyo Main Library moved to Nagatacho in 1961, the year the first stage of construction on its present building was finished. The main building was completed in 1968 and the annex in 1986. Then, in October 2002, the Kansai-kan opened in Kansai Science City, in the town of Seika in Soraku District, Kyoto Prefecture. That was the same year the International Library of Children's Literature fully opened. Today the NDL has three facilities: the Tokyo Main Library, the Kansai-kan, and the International Library of Children's Literature in Ueno.

A library for the Diet

As its name suggests, the library's first job is to serve the Diet. At the center of that work is the Research and Legislative Reference Bureau, which works on the principle of nonpartisanship and keeps its research confidential. The library also brings its services to the executive and judicial branches through 27 branch libraries located in their agencies.

The National Diet Library Law also sets up the legal deposit system, which requires every publication issued in Japan to be deposited with the library. For a privately published item, the publisher deposits one copy within 30 days of publication. The rule isn't limited to books, magazines and newspapers; it also covers CDs, DVDs, records, sheet music, maps and more.

At the end of March 2025, the collection held about 12.47 million books, about 21.18 million magazines and newspapers, and about 14.46 million other, non-book materials.

The Digital Collections, no visit needed

If you visit in person, the rules as of July 2025 say you generally need to be 18 or older to enter the Tokyo Main Library and use its materials. Anything you use there has to stay in the building. That's where the National Diet Library Digital Collections come in handy, letting you see materials without making the trip. The service lets you search and view the digital materials the library has gathered and preserved, and for items whose copyright has expired, among others, you can see the full page images online.

If you want to use an image, look at the access level shown for each one. When it says the image is online because its copyright has expired, you can use it freely without applying to the library, and there's no fee. For images that are online under an official ruling or by permission, and others like them, you need the copyright holder's permission to use them. Even when a whole item is out of copyright, the access level can differ from image to image, so check each image you want to use.

There's no set way to credit the source; something like "From the National Diet Library Digital Collections" is enough. Even with items whose copyright has expired, though, you're still expected to respect the author's moral rights, which protect the honor and intentions of the person who made the work, and to be mindful of privacy and similar concerns.

If you'd simply like to browse old photos and nishiki-e, Japan's multicolored woodblock prints, at your leisure, try the online exhibition "Exploring Japanese Landmarks in Nishiki-e and Photographs," released on March 26, 2024. It presents nishiki-e from the Edo period alongside photographs printed in Meiji and Taisho books of the late 1800s and early 1900s, arranged by famous places around Japan. Every image in the exhibition is in the public domain, and both the images and the commentary can be copied and reused, including for commercial purposes, without applying to the library.

How it connects to 3rd-Party.jp

Kioku Kabegami launched in 2026 as the first project from 3rd-Party.jp, which takes public material that sits unnoticed online and tidies it up so it's easy to find and easy to use every day. We began gathering our old photos and nishiki-e from the National Diet Library's collections. From the items available online because their copyright has expired, we go through photo albums and prints one by one and pick the ones that look good as a wallpaper and have little damage or blur. The only changes we make to the original image are straightening it and tidying the margins. We never paint anything in or take anything out. Depending on the photo, its page links to either the Digital Collections or the online exhibition, so you can compare it with the original.

Sources

• National Diet Library, “History” (Japanese)
• Kotobank, Nihon Daihyakka Zensho, “National Diet Library” (Japanese)
• National Diet Library 70th anniversary exhibition, timeline (Japanese)
• National Diet Library 70th anniversary exhibition, “The NDL in the Showa Era” (Japanese)
• National Diet Library, keynote report for the 29th China–Japan exchange (Japanese)
• National Diet Library, pamphlet (Japanese)
• International Library of Children’s Literature, “History of the Building” (Japanese)
• National Diet Library, “Services for the Diet” (Japanese)
• National Diet Library, “Organization”
• National Diet Library, pamphlet “Legal Deposit System” (Japanese)
• National Diet Library, “Legal Deposit System” (Japanese)
• National Diet Library, “For Visitors under 18” (Japanese)
• Tokyo Main Library user guide, as of July 2025 (Japanese)
• National Diet Library, “Information for Visitors” (Japanese)
• National Diet Library, “Web Services” (Japanese)
• National Diet Library, FAQ “Digitization of Materials” (Japanese)
• National Diet Library, “Reusing Content from the Website” (Japanese)
• National Diet Library, FAQ “Reusing Content from the Website” (Japanese)
• National Diet Library, Current Awareness Portal (Japanese)
• National Diet Library online exhibition, “About”