Shigeo Odachi graduated from Tokyo University with a degree in political science (1916).
Shigeo Odachi rose to the post of Deputy Manager of the Local Affairs Bureau, and was appointed governor of Fukui Prefecture in 1932. In 1934, Odachi was appointed Secretary of Internal Affairs and Communications of the Management and Coordination Agency of Manchukuo. He assisted Naoki Hoshino is developing the first Five-Year Plan for Manchukuo, which had a strong emphasis on the development of heavy industry. He returned to Japan in 1939, and served as a bureaucrat in the Home Ministry during the administrations of Nobuyuki Abe and Mitsumasa Yonai.
Following the start of World War II, in 1942 Odachi was appointed civilian mayor of "Syonan" (Singapore) under Japanese occupation.
Odachi returned to Japan in 1943, and with the amalgamation of Tokyo City and Tokyo-fu into Tokyo Metropolis, he became the first Administrator of Tokyo, a position equivalent to the present Governor of Tokyo. As the war situations was quickly deteriorating for Japan, and Tokyo came under increasing thread of attack, he organized the evacuation of children from Tokyo. In September 1943, he gave the order to destroy all of the animals at Ueno Zoo, an act recounted in the post-war book Faithful Elephants. In July 1944, he was asked to join the cabinet of Prime Minister Kuniaki Koiso as Home Minister. Odachi was awarded the 1st class of the Order of the Sacred Treasures on September 12, 1944.
After the surrender of Japan, Odachi was, was purged from public office by orders of the American occupation authorities. However, he was never arrested for war crimes. In 1953, he ran for a seat in the post-war upper house of the Diet of Japan, under the Liberal Party banner.
With the support of Chief Cabinet Secretary Taketora Ogata, Odachi joined the 5th Yoshida administration as Minister of Education in 1953. He was instrumental in framing and passing the Education Bill which controls the political activities of schoolteachers.