A valve device includes: a casing having an outflow port in which a fluid outlet opening is formed; a joint joined to an opening end surface of the outlet opening; a valve accommodated in the casing so as to be rotatable or slidable and in which a communication port that can communicate with the outlet opening is formed; and a sliding ring with a sliding surface for sliding on an outer surface of the valve while being accommodated in the outflow port and communicates the outlet and the communication port based upon a position of the valve. At least the outer surface of the valve includes a first resin material that contains a first resin, at least the sliding surface of the sliding ring includes a second resin material that contains a second resin, and the first resin and the second resin are the same type of resin.