A fuel shutoff valve includes a valve, a float, and an auxiliary member. The valve is configured to open or close an air passage of a fuel tank. The float floats on fuel and moves in a valve closing direction to close the valve, or in a valve opening direction opposite to the valve closing direction to open the valve. The auxiliary member has a predetermined weight, and abuts on the float to apply a weight on the float in the valve opening direction, or separating from the float not to apply the weight on the float in the valve closing direction.