Italy's Elena Fanchini was second in 1:40.16 and Renate Goetschl of Austria won the bronze medal with 1:40.29.
Kostelic thus claimed her second gold medal of the ongoing world Alpine ski championships. On Friday the 23-year-old best Croatian skier won the combined,
Kostelic has so far won three Olympic gold medals, in giant slalom, slalom and combined, and one silver in super-G which she won at the 2002 Olympic Games at Salt Lake City, the United States.
Besides, Janica has also gold medals from the 2003 World Championships in combined and slalom.
She has 20 World Cup wins: 20 (slalom 17, combined 3).
She was also the overall champion in the World Cup in 2003 and 2001, and slalom champion 2003 and 2001.
At the ongoing World Championships, Janica will compete in giant slalom on Tuesday, 8 February.