An air-conditioning apparatus, comprising: - an outdoor unit including a compressor and an outdoor heat exchanger; - a plurality of indoor units each including an indoor heat exchanger; and - a relay unit configured to distribute refrigerant supplied from the outdoor unit to the plurality of indoor units, the relay unit including: - a first branch unit in which liquid-side pipes connected to the plurality of indoor units join together; and - a first refrigerant shutoff valve configured to control bidirectional flow of the refrigerant, and provided to the first branch unit, a number of the first refrigerant shutoff valve being smaller than a number of the plurality of indoor units, - a second branch unit in which gas-side pipes connected to the plurality of indoor units join together, characterised by further comprising: - a plurality of second refrigerant shutoff valves configured to control the bi-directional flow of the refrigerant, wherein each gas-side pipe has a second refrigerant shutoff valve of the plurality of second refrigerant shutoff valves arranged thereon; wherein the outdoor unit further includes a flow switching unit configured to switch a direction of flow of the refrigerant, the air-conditioning apparatus further comprises: - a refrigerant leakage detecting unit configured to detect leakage of the refrigerant; and - a control unit configured to, when the leakage of the refrigerant in at least one of the plurality of indoor units is detected by the refrigerant leakage detecting unit, control the flow switching unit so that the outdoor heat exchanger serves as a passage functioning as a condenser, and closes the first refrigerant shutoff valve and the second refrigerant shutoff valve corresponding to the indoor unit in which the leakage is detected. - an outdoor unit including a compressor and an outdoor heat exchanger; - a plurality of indoor units each including an indoor heat exchanger; and - a relay unit configured to distribute refrigerant supplied from the outdoor unit to the plurality of indoor units, the relay unit including: - a first branch unit in which liquid-side pipes connected to the plurality of indoor units join together; and - a first refrigerant shutoff valve configured to control bidirectional flow of the refrigerant, and provided to the first branch unit, a number of the first refrigerant shutoff valve being smaller than a number of the plurality of indoor units, - a second branch unit in which gas-side pipes connected to the plurality of indoor units join together, characterised by further comprising: - a plurality of second refrigerant shutoff valves configured to control the bi-directional flow of the refrigerant, wherein each gas-side pipe has a second refrigerant shutoff valve of the plurality of second refrigerant shutoff valves arranged thereon; - a first branch unit in which liquid-side pipes connected to the plurality of indoor units join together; and - a first refrigerant shutoff valve configured to control bidirectional flow of the refrigerant, and provided to the first branch unit, a number of the first refrigerant shutoff valve being smaller than a number of the plurality of indoor units, - a second branch unit in which gas-side pipes connected to the plurality of indoor units join together, characterised by further comprising: - a plurality of second refrigerant shutoff valves configured to control the bi-directional flow of the refrigerant, wherein each gas-side pipe has a second refrigerant shutoff valve of the plurality of second refrigerant shutoff valves arranged thereon; - a plurality of second refrigerant shutoff valves configured to control the bi-directional flow of the refrigerant, wherein each gas-side pipe has a second refrigerant shutoff valve of the plurality of second refrigerant shutoff valves arranged thereon; wherein the outdoor unit further includes a flow switching unit configured to switch a direction of flow of the refrigerant, the air-conditioning apparatus further comprises: - a refrigerant leakage detecting unit configured to detect leakage of the refrigerant; and - a control unit configured to, when the leakage of the refrigerant in at least one of the plurality of indoor units is detected by the refrigerant leakage detecting unit, control the flow switching unit so that the outdoor heat exchanger serves as a passage functioning as a condenser, and closes the first refrigerant shutoff valve and the second refrigerant shutoff valve corresponding to the indoor unit in which the leakage is detected. - a refrigerant leakage detecting unit configured to detect leakage of the refrigerant; and - a control unit configured to, when the leakage of the refrigerant in at least one of the plurality of indoor units is detected by the refrigerant leakage detecting unit, control the flow switching unit so that the outdoor heat exchanger serves as a passage functioning as a condenser, and closes the first refrigerant shutoff valve and the second refrigerant shutoff valve corresponding to the indoor unit in which the leakage is detected.