A valve device includes a housing, a valve member, a valve seat member, a fixing member for fixing the valve seat member to the housing, and a housing-side seal portion. The housing has a valve chamber, and a housing-space inner wall forming a housing space communicating with the valve chamber. The housing-side seal portion blocks a flow of fluid between the valve seat member and the housing-space inner wall. The valve seat member has a tubular portion and a flange portion connected to the tubular portion. The flange portion is interposed between a facing surface of the housing-space inner wall and the fixing member in an axial direction. The fixing member is fixed to the housing-space inner wall in an airtight state. The housing-side seal portion is made of a rubber material and is interposed between the flange portion and the fixing member.