To provide a cooling device capable of avoiding the contact of atmosphere and brine as much as possible and reducing the usage of the brine.

The cooling device includes a brine circulation path 30 having a heat exchanger 31 for heat-exchanging a cold temperature refrigerant of a refrigerator 20 and the brine and cooling the brine, a brine tank 32 for storing the brine cooled in the heat exchanger, a brine supply path 35 for supplying the brine inside the brine tank through a circulation pump 33 to a cooling circuit 34 of a heating element 12, and a brine recovery path 36 for recovering the brine from the cooling circuit of the heating element to the heat exchanger. In addition, a reserve tank 27 is provided above the brine tank, and a gas discharge path 38 connecting the upper part of the brine tank and the upper part of the reserve tank and a brine replenishing path 39 connecting the lower part of the brine tank and the lower part of the reserve tank are provided between the reserve tank and the brine tank.