On February 5, 2000, Inamoto debuted for the Japan national team under manager Philippe Troussier against Mexico. After the debuted, Inamoto played 10 matches or more every year. In September 2000, Inamoto was selected Japan U-23 national team for 2000 Summer Olympics. He played full-time in all 4 matches and scored a goal against Slovakia. In 2000, Inamoto played at 2000 Asian Cup. He played four matches while Japan won the championship. In 2001, he also played at 2001 Confederations Cup. He played four matches and Japan came second place. In 2002, he was selected Japan for 2002 World Cup. He played all four matches and scored two goals against Belgium at first match and Russia at second match. Japan qualified to the knockout stage first time in Japan's history. After 2002 World Cup, Inamoto played at 2003 and 2005 Confederations Cup. In 2006, he was selected Japan for 2006 World Cup. He played two matches while Japan was eliminated in the group stages. After 2006 World Cup, Inamoto was not selected Japan 1 year for generational change. In June 2007, he played for Japan for the first time in a year. After that, he played several matches every year. In 2010, he was selected Japan for 2010 World Cup. He played two matches and Japan qualified to the knockout stage. This World Cup is his last game for Japan. He played 82 games and scored 5 goals for Japan.