Provided a valve unit (100) used for a heat-pump system, comprising: at least one liquid refrigerant pipe portion (210, 211); at least one gas refrigerant pipe portion (220, 221, 230, 240, 241); at least one liquid control valve (264) disposed in the liquid refrigerant pipe portion; at least one gas control valve (261, 262, 265) disposed in the gas refrigerant pipe portion; a casing (300) accommodating at least the liquid control valve and the gas control valve; and an air-discharge mechanism (500) configured to operate to discharge an air in an internal space (301) of the casing to an external space outside the casing when a refrigerant leakage in the casing has occurred.