This invention relates to a gasification process for a coal gasification furnace which comprises ejecting coal and an oxidizing agent along the circumferential direction of a gasification chamber (10) to form a whirling stream, making the two contact and react with each other in the gasification chamber (10), thereby producing a combustible gas from the coal while making ash in the coal melt into the form of slag, and withdrawing the slag through a slag tap (3) provided at the lower part of the gasification chamber (10) into a slag cooling chamber, wherein said process comprises causing the whirling stream to produce pressure difference such that the pressure decreases from the wall surface of the gasification chamber (10) toward the central part thereof, forming, by use of the pressure difference, a recycle system wherein a part of the combustible gas produced is introduced from the gasification chamber to the slag cooling chamber and returned again therefrom to the gasification chamber (10), and heating the slag tap (3) by means of the circulating combustible gas, and to a process therefor.