A vehicle-mounted cooling system includes an air-conditioning refrigerant circuit including a refrigerant passage, a compressor, a heat source-side heat exchanger and a use-side heat exchanger, a battery, and a battery cooling unit cooling the battery using the refrigerant. A control device controls a drive state of the compressor in response to an air-conditioning request and a battery cooling request. The control device includes an abnormality determination unit configured to determine whether an abnormality has occurred in the air-conditioning refrigerant circuit, and a control mode change unit configured to perform, under a situation where the battery cooling request has occurred and it is determined that an abnormality has occurred in the air-conditioning refrigerant circuit, a change of a refrigerant-circulation control mode while permitting the battery cooling unit to continuously cool the battery based on the refrigerant, the refrigerant-circulation control mode representing how the refrigerant is circulated in the air-conditioning refrigerant circuit.