<p>Provided is a heat spreader for a semiconductor device, by which many pin-like fins are bonded not to be easily broken even when the pins are incorporated into a semiconductor device heat dissipating structure which performs cooling with air. A heat spreader (1) for a semiconductor device is provided with a plurality of columnar members (12) bonded on one surface of a board-like member (11), and a bonding layer (15) formed between the board-like member (11) and the columnar member (12). The board-like member (11) is composed of a composite material containing a matrix made of aluminum (111) and silicon carbide particles (112) dispersed in the matrix. The columnar member (12) is composed of a material containing aluminum. The ratio of an area where the aluminum (111) exists within one surface of the board-like member (11) is 30% or more, and the effective maximum length of the silicon carbide particles (112) is 10% or less of the diameter of a circle equivalent to the area of a projection flat surface obtained when a bonding interface (14) is projected onto one surface of the board-like member (11).</p>
