Yamauchi was born in Tokyo in 1943. He graduated from the Takinogawa Daiyon Elementary School and Kita Ward Shinmachi Junior High School (currently Tabata Junior High School). At the Tamagawa University, he meet , a fellow classmate and latter became his friend. His older brother was an actor for . Yamauchi's height was 170 cm his blood was Type A. In 1955, he made his debut as a under the stage name "Ken Kubo" in ""Sugata naki mokugekisha"". Yamauchi would later appeared in Toho's films. On April 1, 1962, he signed a contract with and changed his stage name to "Ken Yamauchi".