Shii became a jockey in 1991 and won his first graded race in 1994 when he won the
Yonsai Himba Tokubetsu with Golden Jack. Shii won his first Grade I race with
Ishino Sunday in 1996 when they won the
Satsuki Shō. Shii became a derby jockey when he won the
Japanese Derby in 2007 with
Vodka. The following year, Shii won the Derby again with
Deep Sky. In 2019, the
Japan Racing Association announced that Shii was to become one of eight individuals who were granted trainer licenses starting from 2020, effectively marking his retirement from jockey that year. Shii officially retired on February 29, 2020. In 2023, Shii would have his first graded race win as a trainer, when won both the Nagoya Daishoten (NAR) and the
Sirius Stakes (JRA) that year. == Major wins as a jockey ==