A heat sink includes a contact portion, a first support rib, a second support rib, a third support rib and a fourth support rib radially extended from the contact portion, and a plurality of parallel fins radially extended from the first support rib, the second support rib, the third support rib and the fourth support rib between two adjacent support ribs. The contact portion contacts with a first heat source. A distance from the contact portion to an edge of the plurality of parallel fins between the first support rib and the second support rib is a first distance. A distance from the contact portion to an edge of the plurality of parallel fins between the third support rib and the fourth support rib is a second distance. The first distance is less than the second distance.