To provide a heat sink which can enhance heat-exchange efficiency and can be easily formed at low cost.

Heat-exchanging fins 3, integrated with a block 2 made of a material with high thermal conductivity, are formed in parallel with each other. Several slots 4 are made in the block 2 so that they are in parallel with each other. The slots 4 are filled with two-phase-condensation fluid 6, and both ends 5A of each slot 4 are blocked. The slots are straight, and the lengthwise direction X of the fins 3 is in parallel with the axial direction Y of the slots 4. The block 2, fins 3, and slots 4 can be easily formed by extrusion molding. The fluid 6 enables uniform, quick heat transfer along the slots 4, enhancing the heat-exchange efficiency.