Refrigerant cycle system and valve device for the same

In a refrigerant cycle system having a hot gas heater function, a valve device includes a solenoid valve (15) for opening and closing a communication between a compressor (10) and a condenser (19), a differential pressure valve (16) opened by a pressure difference between a discharge side of the compressor and an inlet side of the condenser when the solenoid valve is closed for directly introducing gas refrigerant from the discharge side of the compressor into an evaporator (28), and a check valve (21) for preventing refrigerant discharged from the compressor from flowing into the condenser when the solenoid valve is opened. In the valve device, at least the three valves are integrated by a housing member to construct an integrated member.