The invention refers to underground gasification of outcropping coal seams, which is conventionally carried out by means of various processes. In the process according to the inventions a gaseous gasification agent is led to the underground coal and burat together with the coal, whereby a technically utilizable gas is formed and a great amount of sensible heat is obtained in the outflowing gas produced. Depending on its composition, this gas can be used for the purpose of synthesis or as a heating gas with the sensible heat for driving thermal engines.