The purpose of the present invention is to reduce variations in the loads of compressors. A heat source system is configured by connecting in series a plurality of heat source machines respectively having independent refrigeration cycles. The heat source system is provided with: an information acquisition unit (21) which acquires the measured values of the operation frequencies of compressors from the respective heat source machines; a load allotment change unit (22) which changes load allotments currently assigned to the respective heat source machines such that the operation frequencies of the compressors acquired by the information acquisition unit (21) become approximately equal; and a temperature determination unit (23) which sets hot/cold water outlet temperatures of the respective heat source machines according to the changed load allotments.