Renowned originally for his catch wrestling abilities, Kitaoka made his professional debut for Pancrase on October 31, 2000, losing via majority decision. After submitting then 3-0 Kurt Pellegrino, Kitaoka drew with Heath Sims before losing to Katsuya Inoue. After picking up two wins to start 2005, Kitaoka improved to 12-6-8 before he faced future UFC interim welterweight champion Carlos Condit on October 2, 2005. Kitaoka defeated Condit in an upset, submitting him with a heel hook at 3:57 of the first round. A leg lock specialist, Kitaoka would improve to 19-7-9 before facing Katsuya Inoue on January 30, 2008 for the third time after being defeating in their first meeting and a draw in the previous bout. Kitaoka lost via split decision.
After signing with World Victory Road, Kitaoka's first fight for Sengoku was a submission win over Ian James Schaffa at Sengoku 2 on 18 May 2008 before entering Sengoku's eight-man lightweight tournament. In the first round of the tournament at Sengoku 4 on 24 August 2008 he was put up against American Clay French. Kitaoka made short work of French, winning by submission due to an achilles lock at 1:21 of the first round. The win put him up against fellow Japanese fighter Eiji Mitsuoka in the tournament's semifinal taking place at '. Kitaoka again made short work of his opponent winning by a heel hook submission at 1:16 of the first round. The win earned him a place in the tournament's final taking place that same night against Kazunori Yokota. The fight proved longer than Kitaoka's three previous fights as it went the distance completing all three five-minute rounds with Kitaoka being awarded the unanimous decision, thus winning the 2008 Sengoku Lightweight Grand Prix. The Lightweight tournament win set up Kitaoka to fight the last reigning PRIDE Lightweight Champion, Takanori Gomi, for Sengoku's newly created Sengoku Lightweight Championship. The two fought at Sengoku no Ran 2009 on 4 January 2009 and ended with Kitaoka defeating Gomi with an achilles lock at 1:41 of the first round. In his first title defence, on August 2, 2009, at ', Kitaoka lost his lightweight championship to Mizuto Hirota.
Return to Pancrase
Following his title loss in Sengoku, Kitaoka returned to his home promotion Pancrase picking up wins over Jorge Rogrigues and Kuniyoshi Hironaka.
Kitaoka faced former UFC fighter Willamy Freire at DREAM 17. Kitaoka entered the bout on a three fight win streak picking up victories in both Pancrase and DEEP. He won the fight via split decision. Kitaoka faced teammate and fellow Yuki Nakai black belt Shinya Aoki at DREAM's year end event for the DREAM Lightweight Championship. He lost the fight via unanimous decision.
Kitaoka made his debut for Rizin Fighting Federation in 2016. He faced Daron Cruickshank on December 29, 2016, at and won the fight via technical submission in the first round. Kitaoka next faced Yusuke Yachi on July 30, 2017, at. He lost the fight via TKO in the second round. Kitoaka returned at, facing Kiichi Kuniomoto in a catchweight bout of 165 lbs. Kitoka lost via unanimous decision. After picking a first-round heel hook win in Pancrase, Kitaoka returned to the RIZIN ring at RIZIN 11 against Diego Brandao. While attempting a leg lock submission on the ground, Kitoka left himself vulnerable to a flurry of right hands from Brandao on the top, being knocked out just 1:38 into the fight. After losing to Brandao, Kitoaka lost in his fifth defense of his DEEP Lightweight Championship to Koji Takeda via unanimous decision. Kitaoka returned to face Tatsuya Kawajiri at RIZIN: Heisei's Last Yarennoka! for New Year's Eve in 2018. After a fairly impressive performance which included a surprising Kitoka knockdown from a left cross, Kitoaka won via split decision.