An apparatus includes: a cooling medium bath configured to house a first refrigerant in which an electronic device is immersed; a liquid-cooling jacket configured to be provided to the electronic device and to cool the electronic device by a second refrigerant that flows in an internal section of the liquid-cooling jacket; a first pipe coupled to the cooling medium bath, to be immersed in the first refrigerant, and configured to supply the second refrigerant from an outside of the cooling medium bath to the liquid-cooling jacket; a second pipe coupled to the cooling medium bath, to be immersed in the first refrigerant, and configured to discharge the second refrigerant that flows in the internal section of the liquid-cooling jacket to the outside of the cooling medium bath; and a circulator configured to cause the first refrigerant in the cooling medium bath to stream.