Kawashima joined the boxing gym of former WBC and WBA minimumweight champion Hideyuki Ohashi in 1995, and made his professional debut on February 20, 1997, with a 2nd round knockout victory.

He lost a 6-round decision in only his 6th professional fight, but steadily compiled wins to challenge Jesse Maca for the OPBF super flyweight title on December 11, 2000.

On June 23, 2003, Kawashima got his first shot at a world title against WBC and lineal super flyweight champion Masamori Tokuyama, but lost by unanimous decision over 12 rounds.

The rematch was held on January 3, 2007, and Kawashima lost by technical knockout in the tenth round after suffering a knockdown which was regarded as a slip by the referee.

He challenged WBA super flyweight champion Alexander Muñoz as the 7th ranked contender to the title on January 14, 2008, but lost a unanimous decision where he was almost knocked out in the 11th round.