In a land area of 22,634 square kilometers, the diocesan territory covers Saitama, Tochigi, Gunma and Ibaraki prefectures.
In the territory of Saitama diocese, the population is 14,129,148 at end of 2017. Most residents are ethnic Japanese. There are also 260,936 non-Japanese people in the area according to the Immigration Bureau of Japan.
There are many languages/dialects in use in the territory.
The Prefecture Apostolic of Urawa was established on Jan. 4, 1939. It was composed of the four prefectures of Saitama, Tochigi, Gunma, and Ibaraki which were separated from the Diocese of Yokohama. It was entrusted to Canadian Franciscans, and Father Ambrose Leblanc, O.F.M. became the first prefect apostolic. He resigned in 1940, and Father Sakuzo Uchino was appointed the acting ordinary. In 1945 he became prefect apostolic.
Monsignor Uchino resigned in 1957, and on Dec. 16 of the same year the Prefecture Apostolic of Urawa was raised to the status of a diocese. On Dec. 24, 1957, Father Satoshi Nagae was appointed and consecrated the first Bishop of Urawa.
In 1979 Bishop Nagae resigned and on Dec. 20 of the same year Father Kaname Shimamoto was appointed his successor. He was consecrated on March 20 of the following year and became Bishop of Urawa.
On March 20, 1990, Bishop Shimamoto was appointed Archbishop of Nagasaki, and took office in May. After that, Father Hiroshi Oka served as administrator of the diocese until on Sept. 16, 1991, Father Takeo Okada was consecrated and took over as Bishop of Urawa.
On June 12, 2000, Bishop Okada became Archbishop of Tokyo. On the same day, Urawa diocesan priest Father Daiji Tani was appointed Bishop of Urawa. He was consecrated bishop on Sept. 15, 2000.
On March 31, 2003, the diocese of Urawa changed its name. From then on it is called Diocese of Saitama. (Catholic Bishops' Conference of Japan, 2010)
Air planes, railways, buses are the means of transportation in the diocesan area.
According to the Central Intelligence Agency, USA, in 2010, throughout Japan, literacy is 99 percent.