A valve device is attached to a fuel tank. The valve device includes a case including a vent valve port communicating outside of the tank at an upper portion, and including an inflow portion for a fuel below the vent valve port; and an upper floor body inside the case and rising by the fuel flowing into the case to be seated in the vent valve port. In a face portion facing a bottom portion of the upper float body in the case, an elastic piece is formed by a first arc-shaped split groove such that a center side of the face portion becomes a curvature inner side, and a second arc-shaped split groove formed such that a center of the face portion becomes a curvature inner side outside the first arc-shaped split groove. One portion of the elastic piece abuts against the bottom portion of the upper float body.