Yamaguchi was born in Sakawa, Kochi on April 17, 1978. He joined JEF United Ichihara (later "JEF United Chiba") from youth team in 1996. He debuted on March 20, when he was 17 year and 354 days old. It was the youngest player to play for J1 League until Yuki Abe made new record in 1998. He became a regular player as center back from 1997. He moved to Gamba Osaka in 2001. The club won the champions 2005 J1 League, 2007 J.League Cup, 2008 and 2009 Emperor's Cup. He was also elected Best XI for 3 years in a row (2006-2008). In Asia, in 2008, the club won the champions AFC Champions League and the 3rd place Club World Cup. He returned JEF United Chiba in 2012 and played in 3 seasons. He moved to Kyoto Sanga FC in 2015 and retired end of 2015 season.