To provide a heat sink which can prevent deformation of a fin against external force even if the fin is weak, by providing a wall to a heat sink by carrying out bending process to both sides of a base plate, and is excellent in heat dissipation efficiency, and to provide its manufacturing method.

The heat sink consists of a U-shaped base plate formed of two side walls formed by bending process and a plane part positioned in the middle of the two side walls, and a plurality of fins disposed and jointed along the side walls in the plane.