A valve device used by being attached to a fuel tank includes a case provided with an airflow valve opening which communicates with the outside of the tank, on an upper portion, and also provided with a fuel inflow section located on a lower side of the airflow valve opening, and a float body housed in the case so as to be vertically movable, and also seated in the airflow valve opening by being elevated by the fuel flowed into the case through the inflow section. In the case, an airflow section which interconnects the inside of the tank and the inside of the case is formed in a higher side than a waterline of the float body at the seating time, and also at the seating time, this airflow section is restricted.