Over his 16-year career, he played professional baseball in Japan, Canada, Taiwan, Mexico, and South Korea.

Kobayashi graduated from famed baseball-focused PL Gakuen High School in Osaka, where he was a teammate of Kosuke Fukudome, who played for the Chicago Cubs in Major League Baseball.

[citation needed] In 2006, Kobayashi left Japan for Canada to play for the Calgary Vipers of the independent North American League,[1] going 0–2 with a 5.32 ERA for the season.

Returning to Japan in 2007, Kobayashi played for the Kagawa Olive Guyners of the independent Shikoku Island League.

Kobayashi moved to South Korea in 2012 to pitch as a closer for the Goyang Wonders of the KBO Futures League.