An embodiment provides a check valve including a valve case, a positive pressure valve having a resin ring sealing member, and a resin negative pressure valve. The positive pressure valve and the negative pressure valve are disposed in the valve case. The positive pressure valve includes a first mount surface and a second mount surface disposed on an inner diameter side of the first mount surface. In the valve case, a presser cap is mounted on the positive pressure valve so as to sandwich the ring sealing member and the negative pressure valve with the first mount surface and the second mount surface of the positive pressure valve.