In April 1995, Morioka was selected the Japan U-20 national team for 1995 World Youth Championship, but he did not play in the match. On March 31, 1999, Morioka debuted for the Japan national team against Brazil. After the debut, he became a regular player and played all matches including 1999 Copa América in 1999. He mainly played as central defender in three back as Masami Ihara successor. He also served as captain in many matches. In September 2000, he was selected the Japan U-23 national team as over aged player for 2000 Summer Olympics. He played 3 games as captain. In October, he played at 2000 Asian Cup. He played full-time in all 6 matches and Japan won the champions. He also played at 2001 Confederations Cup and Japan won the 2nd place. In 2002, he could not play for injury. He was selected Japan for 2002 World Cup. He played as captain in first match against Belgium, but he was injured and replaced. After 2002 World Cup, in March 2003, he was selected Japan again by new manager Zico. On June 8, 2003, the match against Argentina is his last game for Japan. Although he was a member of Japan for 2003 Confederations Cup in June, he did not play in the match. He played 38 games for Japan until 2003.