At the age of nine, he became a follower of Kobo Taishi (Kiikai).
Shinsho became a priest (821) and lived at the Toji Temple. He was accorded the title of Acharya (843) from Priest Jitsue.
Upon the death of Jitsue, he was made deputy chief priest of Toji. He presided over at Buddhist rites in the Palace on behalf of the head of Toji (854). The same year, he made a statue of Gochi Nyorai (The Buddha of Five Wisdoms), a Buddhist deity, at the Kanshinji Temple in Kawachi Province (Osaka Prefecture) on behalf of Emperor Montoku.
He purchased a mansion in Higashiyama where he built the Zemrinji Temple and set up a Buddhist statue.