He studied agriculture, and worked as a farmer and an agricultural advisor before entering politics.
He served in Parliament as a representative for the Agrarian Party from 1945 to 1958, and then served as Governor of the Province of Lapland from 1958 to 1973. He was awarded the honorary title of Counsellor of State in 1977. He died at the age of 94 in the Kauniainen military hospital near Helsinki in early 2002.
Miettunen served as a cabinet minister for 4,300 days, the eighth-longest period of service in Finnish political history.
He was also known as President Urho Kekkonen"s right-hand manitoba