A cutoff valve having an upstream valve part and a downstream valve part which are assembled in series in a flow passage. Each of the valve elements at the valve parts are formed separably stacking a large diameter first valve element and a small diameter second valve element on each other. The first valve element is formed of elastic material and the second valve element is formed of rigid material. A valve shaft is passed through the center of the first valve element, and the tip of the valve shaft is connected to the second valve element. A first valve element moving component which moves the center part of the first valve element in a direction apart from the second valve element in the state of being engaged with the first valve element when the valve is opened is installed between the first valve element and the valve shaft.