PURPOSE: To provide a coal gasification furnace in which rectangular slag to a burner does not grow and the growth of the slag to a sidewall is prevented to be safely operated.

CONSTITUTION: A gasification furnace is formed in the form of sequentially stacking the combustor 5 of a cross-sectional area A0, a reductor 3a of a cross- sectional area A1 smaller than the A0, and a reductor 3b of a cross-sectional area A2 further smaller than the A1 upward. A burner 2 and a cooling gas injector 7 are mounted on the downward surface of the shoulder of the combustor 5, and a burner 1 is mounted on the downward surface of the shoulder of the reductor 3a. A water-cooled panel 6 is provided on the inner wall of the reductor 3a.