A heat source side controller of an air conditioner has an operating mode allocator and an operating mode setter. The air conditioner has a heat source unit and a plurality of room units. The heat source unit can be switched among a plurality of operating modes having different noise-reduction levels. The operating mode allocator allocates one operating mode to each of the operating room units. The operating mode setter sets the heat source unit to one operating mode from among the plurality of operating modes on the basis of the operating modes allocated by the operating mode allocator to each of the operating room units. In cases in which a specific operating mode is allocated to all of the operating room units, the operating mode setter sets the heat source unit to the specific operating mode.