A fuel valve includes an upper chamber communicating with a ventilation passage of a canister; a lower chamber to be disposed inside a fuel tank; a communicating port between the upper chamber and the lower chamber; and a float member disposed in the lower chamber for blocking the communicating port when fuel flows into the lower chamber. A bottom orifice or a one-way valve is formed in the bottom of the lower chamber for preventing the fuel to flow into the lower chamber and allowing the fuel to flow out from the bottom of the lower chamber. A fuel inlet is formed at a lower side of the side wall to face upwardly to allow the fuel to gradually enter the lower chamber so that an inner pressure in the fuel tank increases by entering the fuel into the lower chamber after the fuel reaches the fuel inlet.