He served as Prefect of Nagoya from 1945, and consecrated Bishop in 1962 when the prefecture was elevated to diocese.

[1][2] Magoshiro Matsuoka was born in Urakami (now part of the city of Nagasaki).

Matsuoka's family practiced Christianity in secret, facing constant persecution and were exiled from their home in 1868 during the fourth Christian purge, escaping to Tsuwano, Shimane until 1873.

Named for his grandfather who died in exile in Tsuwano, Matsuoka entered the Catholic school at Ōura in 1901 and was ordained to the priesthood on February 21, 1918.

[3] Upon Nagoya's elevation to Diocese, Matsuoka received his episcopal consecration on June 3, 1962 at the brand new St. Peter and St. Paul Cathedral from Apostolic Internuncio in Japan, Archbishop Domenico Enrici, with Archbishop Paul Aijirô Yamaguchi and Bishop Paul Yoshigoro Taguchi, as co-consecrators.