Abstract: A cooling device includes a heat receiving unit arranged to contact with a cooling target to receive heat of the cooling target; a heat radiating unit configured to radiate heat of coolant; a tank configured to store therein the coolant; a circulating path configured to circulate the coolant through the heat receiving unit, the heat radiating unit, and the tank; a pump configured to transfer the coolant in the circulating path; and a liquid transfer detecting unit configured to detect liquid transfer of the coolant. The liquid transfer detecting unit includes a detector arranged above a liquid level of the coolant stored in the tank at a position where the coolant having flowed into the tank is hit when the coolant is transferred. The detector is arranged so as to be visible from the outside of the tank.