PURPOSE: To facilitate the evaporation of alcohol to promote its conversion in a gas engine driven by the converted gas from alcohol by disposing an alcohol evaporator on the way of a cooling water passage.

CONSTITUTION: A cylinder block 52 and a radiator 48 are connected by cooling water pipes 50, 56. Cooling water turned hot after cooling an engine is fed back through the cooling water pipe 56 into the radiator 48. While passing through the pipe 56, the hot cooling water evaporates alcohol in an alcohol evaporator 59 disposed on the way of the pipe 56. Alcohol vapor produced from the evaporator 59 is carried into an alcohol converter 37 which is located in an exhaust manifold 39 and packed with catalyst. Hydrogen and other constituents generated in the converter 37 are supplied for a suction system of an engine via the manifold 39.