PURPOSE: To provide a unit for cooling a heating element with a good cooling effect, by taking air in at a location remote from the heating element.

CONSTITUTION: A cooling unit includes a heat sink body 10 made of good radiating material with a plurality of radiating fins 12 on a base part 11 other than a region of an air duct 20. The air duct 20 has a heat shielding hollow body and is mounted on the air-duct region. The cooling air in the air duct 20 is circulated by an air ventilation unit and blown out through a ventilation hole 21 on a side wall of the air duct 20 to a gap part 12a between the radiating fins 12.