He graduated from Law Department of Tokyo University (1933) and became a diplomatic student secretary of Ministry of Foreign Affairs, assigned to Britain.
Kohei Teraoka was appointed Council at Shanghai (1940), Third Secretary of the Japanese Embassy in Italy (1942) and Second Secretary of the Japanese Legation in Hungary (1943). He was appointed secretary to the Prime Minister (1946) and later in the same year to the Foreign Minister. Kohei Teraoka was appointed director of the Overseas Office at New York (1950) and attended the Peace Conference at San Francisco as suite to the Japanese Delegation (1951). He was appointed Minister and Ambassador to Peru (1957).