A heat sink comprises a plurality of stacked fins being combined. Each fin comprises a plate body with two pairs of locking structures formed symmetrically on two opposite edges of the plate body. Each locking structure comprises an interval part extending integratedly from the plate body, a bearing part depending from the interval part, a lateral position portion and a detaining portion extend continuously from the bearing part. A tab is formed on each detaining portion. The fins are combined in such a manner that the bearing part of each fin bears against an adjacent fin; the plate body of each fin is sandwiched between the bearing part and the detaining portion of each locking structure of an adjacent fin, and between the lateral position portions of a pair of locking structures of the adjacent fin, the tabs of each fin bear against the corresponding interval parts of the adjacent fin.