In a coal gasification furnace adapted to feed pulverized coal thereinto by the use of inert carrier gas and gasify the same, any startup burner can be unnecessitated thereby eliminating any startup combustion chamber. Further, even in the use of a startup burner, it is smaller and lighter in weight than conventional startup burners, allowing the startup combustion chamber to be compact and limiting the height of the entirety of the gasification furnace. As a characteristic feature, a pulverized coal fuel supply passageway (23) to a combustor burner (9) is provided at its midstream portion with a startup gas supply passageway (29) for supply of a startup combustible gas (NG1). After reaching of the temperature of the furnace interior to a first temperature (T1) allowing ignition of pulverized coal with reference to a detected value from furnace interior temperature detecting means (41), transition to combustion by the pulverized coal and carrier gas is effected by increasing the input rate of pulverized coal and carrier gas while decreasing the supply rate of combustible gas (NG1) from the startup gas supply passageway (29).