Belle, who led the majors with 98 home runs for the last two seasons, has signed a a five-year contract with a one-year option.
The signing is a surprise since it was believed the Florida Marlins had the best chance to lure Belle away from the Cleveland Indians. The Marlins offered Belle a four-year contract, worth $38m.
The White Sox owner and chairman, Jerry Reinsdorf, said: "Money wasn't what it was all about, although this contract makes him the highest-paid player in baseball. He signed with us because he likes playing in Chicago and batting behind Frank Thomas."
Belle said: "It was important for me to stay in the American League. I like the way the organisation is emphasising a championship. Frank Thomas is a good friend of mine and I know he had some influence in getting me over here."
Belle last week rejected the Indians' five-year offer, worth $40m.