The heat sink fastener includes a heat conductive board and a flexible metallic wire. The heat conductive board has a pair of pivot portions. The flexible metallic wire has a pair of flexible arms and a middle portion connecting therebetween. Each flexible arm connects to the pivot portion. The pivot portion side of the heat conductive board is formed with a blocking sheet. The middle portion is provided with a bend for being blocked by the blocking sheet. When the flexible metallic wire is hooked to a ring on a circuit board, it will generate pressure to the heat conductive board resulting from the bent flexible arms and the blocked middle portion.