He competed in four Winter Olympics from 1960 to 1972. He won seven medals at the first three of them. This makes him one of the most successful skiers in Finland. His success at the 1964 Winter Olympics earned him the nickname "Mister Seefeld". The Finnish Ministry of Education honored him with the Pro Urheilu letter of recognition in 2000. There is a museum called Mäntyranta in Pello.
Mäntyranta died on 30 December 2013 from a heart attack. He died in Pello, aged 74.