A heat sink including a base section, connection fins, and parallel fins. The base section includes: a first base plate configured to be mounted with a heat generating component on its outer surface; a second base plate disposed to face the first base plate in a parallel manner, configured to be mounted with a heat generating component on its outer surface; and a third base plate disposed perpendicular to the first base plate and the second base plate, which secures the first base plate and the second base plate along a junction line. The base section includes first and second regions arranged in the direction of the junction line. The connection fins are disposed on the first region to connect inner surfaces of the first and second base plates and to be parallel to the third base plate, and the parallel fins are disposed on the second region from an inner surface of the third base plate to be parallel to the first base plate.