A heat sink for an electronic component cooling apparatus being small in size and having reduced weight, being capable of coping with increasing amounts of heat generation from the electronic component and capable of performing high cooling efficiency. A plurality of radiation fins 3 surrounding an impeller of a fan are mounted on a side of a base 2 of a heat sink 1. A heat conductive thick portion comprising linear ribs 4 and an annular rib 5 is formed on the base 2 where it is surrounded by the radiation fins 3. The linear ribs 4 and the annular rib 5, having more thickness than the radiation fin mounting area 6, are formed of a pattern that can reduce the resistance of heat transfer between a heat source opposed-portion 7, which opposes to the heat source of the electronic component and the radiation fin mounting area 6.