Shimokawa was born in Gifu on May 14, 1970. After graduating from Gifu Technical High School, he joined Furukawa Electric (later "JEF United Ichihara") in 1989. From first season, he played as regular goalkeeper over 10 seasons. In 2000, his opportunity to play decreased behind Ryo Kushino. He moved to Yokohama F. Marinos in 2001. However, there were few opportunities to play in the match. His only match in the J1 League at Yokohama F. Marinos is last game in 2003 season. In this match, he played instead Tetsuya Enomoto was shown a red card in the 15th minute. Marinos won this match and won the J1 League champions in this season. He retired end of 2006 season.