Aoki was born in Takasaki on September 28, 1982. After graduating from Maebashi Ikuei High School, he joined J1 League club Kashima Antlers in 2001. He played as defensive midfielder from first season and Antlers won the champions in 2001 J1 League and 2002 J.League Cup. He became a regular player from 2003 season and played many matches for a long time. In 2007, Antlers won the champions in J1 League for the first time in 6 years and Emperor's Cup. Antlers won the champions in J1 League for 3 years in a row (2007-2009). From 2010 season, although his opportunity to play as starting member decreased, Antlers won the champions 2010 Emperor's Cup, 2011 and 2012 J.League Cup. From 2012, he played many matches as center back. Antlers won the champions in 2015 J.League Cup. However he could hardly play in the match in 2016. In July 2016, Aoki moved to Sagan Tosu. He played for the club in 2 seasons. In 2018, he moved to J2 League club Roasso Kumamoto. In 2019, he moved to Prefectural Leagues club Nankatsu SC.