PURPOSE: To prevent the fuel from flowing into the evaporation tube and others by arranging a valve body closing the outlet in response to the rise of the fuel surface in the fuel outlet provided in the bottom plate of the separation chamber.

CONSTITUTION: The separation chamber 12 is fixedly provided to the upper wall 11 inside the fuel tank 5. The fuel chamber body 12' has the evaporation tube 13 in its upper part, inlet 14 for the evaporative fuel in its side wall and fuel outlet 15 in the bottom plate. The float-like valve body 16 consists of the disc- like main body 161 and the holder part 162. The valve body 16 moves upward in response to the rise of the fuel surface to close the outlet 15 to shut off the fuel flow. When the fuel surface is lowered, the valve body 16 goes down and the fuel is returned to the fuel tank 15. Therefore, the fuel flow into the evapporation tube and the resulting contamination of the canister and others can thus be prevented.