An air-conditioning system having exceptional security is provided. An air-conditioning system comprises a plurality of indoor units installed in a target space, a controller configured and arranged to control the actions of the plurality of indoor units, and a refrigerant leakage sensor configured and arranged to sense refrigerant leakage in the target space. Each of the indoor units has indoor fan. When the refrigerant leakage sensor has sensed refrigerant leakage, the controller configured and arranged to cause the indoor fan of the indoor unit that has received a refrigerant leakage signal to be driven at a predetermined first rotation speed, and cause the indoor fan of other indoor unit (emergency group indoor units) belonging to the same group as the aforementioned indoor unit to be driven at a predetermined second rotation speed.