Abstract: A valve device includes main valve element and pilot valve element. The main valve element divides valve element space of housing into first pressure chamber and second pressure chamber. The pilot valve element is provided in the second pressure chamber. In one example, first pilot passage including first restrictor extends from primary passage to the second pressure chamber, and second pilot passage including second restrictor is formed at the main valve element. The main valve element and the pilot valve element are coupled to each other by pin, and gap is formed between the pin and one of the main valve element and the pilot valve element. The pilot valve element opens and closes the second pilot passage by biasing member and drive mechanism. The main valve element is driven so as to open the secondary passage by differential pressure between the first pressure chamber and the second pressure chamber.