PURPOSE: To provide a heat sink for cooling a semiconductor device without increasing its size by producing uniform flow velocity of air through all fins to maximize the cooling effect of the fins.

CONSTITUTION: A heat sink has a base 4 in the form of a plate or bar, from which a plurality of fins 5 of different thicknesses extend at regular intervals. The fins are thickest at both ends and thinnest at the center. Therefore, the distance between faces of adjacent fins becomes wider toward the center. This increases the flow velocity of air through the middle fins, thereby improving the cooling characteristic.