PURPOSE: To supply fuel to a fuel circuit without degrading the composition of a fuel mixture for internal combustion engine by forming a fuel device, which captures the fuel vapor and supplies fuel to the fuel circuit from a gas exhaust pipeline, as a liquefying device to inversely convert the vapor into the liquid phase.

CONSTITUTION: A pressure sensor 3 to detect the vapor pressure of a fuel is accommodated at the ceiling 1 of a fuel tank 2 installed in a car, and when the pressure exceeds a predetermined amount, a motor 4 is started by a signal processing electronic device connected with the sensor 3 so that a compressor 5 is actuated. The compressor 5 sucks out the fuel vapor until the pressure sinks below the second value predetermined and compresses isotropically for liquefaction of the vapor sucked in at this stage of work, and the liquefied substance is collected at the bottom 10 of a pressure chamber 9. The motor 4 is turned off on the basis of the output of a level meter 12 or a pressure sensor 16. At the same time, a solenoid valve 17 provided in a collecting line 18 at the chamber bottom 10 is opened so that the fuel is supplied to the suction line of the fuel pump.