A cooling unit has a heat receiving unit that receives heat from a body radiating heat; a radiator disposed at a distance from the heat receiving unit and radiating recovered heat; a liquid coolant transporting heat generated at the heat receiving unit to the radiator; and a hollow tube disposed so that the liquid coolant circulates between the heat receiving unit and the radiator, a circulating flow of the liquid coolant formed by an elevating force of air bubbles generated from the heat received at the heat receiving unit, the radiator having an air pocket forming one part of the circulation path of the liquid coolant together with the hollow tube and capable of collecting the air bubbles.