A control apparatus for a multi-room air conditioner having a heat source unit, and a plurality of conditioning units connected to the heat source unit via a refrigerant communication tube (17a, 17b) and distributed among a plurality of rooms (R1, R2..., Rn); said control apparatus for a multi-room air conditioner being characterized by comprising: a heat source unit that can be switched among a plurality of operating modes having different noise-reduction levels; an operating mode allocator for allocating one operating mode from among the plurality of operating modes to each of the operating conditioning units of the plurality of conditioning units; and an operating mode setter for setting 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 conditioning units; wherein the plurality of operating modes includes a first operating mode, a second operating mode and a third operating mode whose noise-reduction levels are higher than in a regular operating mode, wherein the second noise-reduction operating mode has a higher noise-reduction level than the first noise-reduction operating mode, and the third noise-reduction operating mode has a higher noise-reduction level than the second noise-reduction operating mode; under a first condition in which a specific operating mode from among the plurality of operating modes is allocated to all of the operating conditioning units, the operating mode setter sets the heat source unit to the specific operating mode; and under a second condition in which the second operating mode is allocated to at least one of the operating conditioning units, and all of the required performances of the rooms (R1, R2,... Rn) in which the remaining conditioning units of the operating conditioning unit are installed are less than a specific value, the operating mode setter sets the heat source unit to the second operating mode. a heat source unit that can be switched among a plurality of operating modes having different noise-reduction levels; an operating mode allocator for allocating one operating mode from among the plurality of operating modes to each of the operating conditioning units of the plurality of conditioning units; and an operating mode setter for setting 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 conditioning units; wherein the plurality of operating modes includes a first operating mode, a second operating mode and a third operating mode whose noise-reduction levels are higher than in a regular operating mode, wherein the second noise-reduction operating mode has a higher noise-reduction level than the first noise-reduction operating mode, and the third noise-reduction operating mode has a higher noise-reduction level than the second noise-reduction operating mode; under a first condition in which a specific operating mode from among the plurality of operating modes is allocated to all of the operating conditioning units, the operating mode setter sets the heat source unit to the specific operating mode; and under a second condition in which the second operating mode is allocated to at least one of the operating conditioning units, and all of the required performances of the rooms (R1, R2,... Rn) in which the remaining conditioning units of the operating conditioning unit are installed are less than a specific value, the operating mode setter sets the heat source unit to the second operating mode.