Kazunari Watanabe specializes in short-term events in track cycling. Several times he finished in the team sprint podium at World Cup races. In 2004 he won silver in this event in Moscow, as in 2005 in Sidney. Followed in 2006 gold medal at the Asian Games in Doha, along with Kazuya Narita and Yudai Nitta. 2008 in Copenhagen followed again silver. In 2010 he finished third in the team sprint at the Asian Games in Guangzhou second place, with Narita and Nitta. In the UCI Track World Championships 2011 in Apeldoorn, he was with Nitta and Kazuka Amagai Tenth, a year later at the World Championships in Melbourne with Amagai and Seiichiro Nagakawa fourth. Also in 2012 he became Asian champions in the sprint.
2008 Watanabe started in the Olympic Games in Beijing in the sprint ( 12th place) and in the team sprint ( 6th place).