A heat sink fixing device for fixing a heat sink on a printed circuit board is disclosed. The fixing device comprises a connecting portion fixed on one side of the heat sink, an extension portion connected with the connecting portion, a first pin extended downward from partial lower edge of the extension portion for plugging into the printed circuit board, and a second pin extended downward from partial lower edge of the connecting portion and connected with the first pin for plugging into the printed circuit board. The heat sink fixing device can strengthen the pin structure, increase the tin soldering area and fix the heat sink on the printed circuit board firmly.