Yamamoto competed at the 2004 Summer Olympics in men's individual archery.

In the quarterfinals, Yamamoto faced Im Dong-hyun of South Korea, defeating the 1st-ranked archer 111–110 in the 12-arrow match and advancing to the semifinals.

There, he faced Tim Cuddihy of Australia, defeating the eventual bronze medalist in a 10–9 tie-breaker after the first 12 arrows resulted in a 115–115 tie.

Since 2004 Yamamoto has been a frequent guest on television programs in Japan and has become a well recognized public figure.

Yamamoto was also a member of the 8th-place Japanese men's archery team at the 2004 Summer Olympics.