On March 3, 1964, when Kamamoto was a Waseda University student, he debuted and scored a goal for the Japan national team against Singapore. In October, he was selected by Japan for 1964 Summer Olympics in Tokyo. He played all matches and scored 1 goal. In 1968, he also was selected Japan for 1968 Summer Olympics in Mexico City. Japan won Bronze Medal and he became a top scorer. He played all matches and scored 7 goals. In 2018, this team was selected Japan Football Hall of Fame. In the 1970s, after many Olympic players left national team, he continued being selected national team. He also played at 1966, 1970 and 1974 Asian Games. In 1977, he retired from national team. He played 76 games and scored 75 goals for Japan until 1977.