A heat sink for cooling an electronic component includes a lower plate, an upper plate, an upper fin set and a lower fin set respectively fixed on the upper plate and the lower plate, and a plurality of heat pipes sandwiched between the upper plate and the lower plate. The lower plate forms a protrusion projecting downwardly therefrom. A bottom surface of the protrusion is milled to be flat and smooth, whereby the bottom surface can intimately contact the electronic component. A method for manufacturing the heat sink comprising milling a bottom surface of a protrusion punched downwardly from a lower plate, whereby the bottom surface can be flat and smooth sufficiently to have an intimate contact with an electronic component, and sequentially welding an upper plate on the lower plate and a plurality of fins on the lower plate and the upper plate, respectively.