Hailing from Ōbatake, Yamaguchi, Tanaka established himself domestically with back-to-back decathlon wins at the Japanese Athletics Championships in 2004 and 2005.

[1] On his first international appearance, he won the bronze medal at the 2005 Asian Athletics Championships, finishing behind Pavel Andreev and Kim Kun-Woo.

He scored a personal best total of 7803 points for decathlon in Kanazawa in June 2006,[4] but at his first Asian Games that year he was far off this form and, after he failed to produce a mark in the pole vault, he finished in tenth place.

[5] As the reigning national champion, Tanaka gained selection for the 2007 World Championships in Athletics, held in Osaka, and he finished in 19th place overall.

[7] In the absence of Dmitriy Karpov and the defending champion Ahmed Hassan Moussa, he won the 2009 Asian Athletics Championships.