VALVE DEVICE

There is provided a valve device, including: a housing; a float valve; and a seal member. An opening portion includes a first region, and a second region. The seal member includes a first cover portion, and a second cover portion. The second cover portion includes a support portion, a wide portion, and a narrow portion. In a state where the seal member is retained and supported by the support portion with respect to the float valve, a width of the wide portion is set such that a tip end of the second region is covered, and that the second region of the opening portion is not exposed out of the seal member even in a state where the seal member is maximally displaced in a radial direction and/or a peripheral direction of the housing with respect to the opening portion.