PURPOSE: To greatly improve a measuring accuracy of fuel supplied in an intake passageway and to realize an air-fuel ratio control.

CONSTITUTION: This device is provided with an intake passageway 18a connected to an intake port communicating with an interior of a cylinder, a fuel storage room 80 supplied with fuel from an outside fuel supply system, a pressure room 84 communicating with the storage room 80 via a fuel introduction port 83 and with the intake passageway 18a via a fuel discharge port 87, an introduction-side check valve 85 allowing only a flow to the pressure room 84 from the fuel storage room 80, and heating members 86a, 86b which produce bubbles to reduce a substantial volume of the pressure room 84 when they are energized.