PURPOSE: To perform driving of an engine in high combustion efficiency, by vaporizing liquid fuel with a heating carburetor device, obtaining gas fuel and driving the engine with the gas fuel.

CONSTITUTION: When an engine is started, if an engine switch 18 is closed, gasoline in a fuel tank 1 is fed to the engine 5 via an outflow pipe 2 and solenoid valve 3, and the engine 5 can be started as usual. A heat radiator 14, provided in the way of an exhaust pipe 13, is increased its temperature by operation of the engine 5, and gasoline, in a heating gasifier chamber 6 provided with the heat radiator 14, can be heated. This gasoline vapor then flows into a vapor accumulator chamber 10 through a vapor outflow pipe 9. Here the gasoline vapor, if reaching prescribed pressure, can be fed to the engine 5 instead of liquid gasoline by closing the solenoid valve 3 while opening a solenoid valve 12 with action of a pressure switch 15.