In 1900, he graduated from the law department of Tokyo Imperial University, and found employment as a journalist for magazines.

He was elected to a seat in the Tokyo City assembly in 1903; however, in 1905 he accepted a position as a lecturer at a law school in Yunnan Province, China.

In 1931, Prime Minister Tsuyoshi Inukai selected Shimada as Director-General of the Cabinet Legislation Bureau.

As with all other Japanese politicians, Tawara was forced to join the Taisei Yokusankai created by Konoe in 1940.

During World War II, Shimada accepted the cabinet position of Minister of Agriculture and Commerce under the Koiso administration.