To release heat generated by a semiconductor which is arranged on a closely packed substrate by a small device, at low cost and efficiently.

The heatsink device is provided with the substrate 10 on which the semiconductor 1 is mounted and in which a heat radiation path (via holes 11 and 14 and an internal copper foil pattern 12) is formed for leading heat conducted from the backside of the semiconductor 1 to lead-out positions on the periphery of the semiconductor 1, a heat dissipation fin 25 which radiates heat conducted from the surface of the semiconductor 1, and a fin fixing metal fixture 20 which is formed of a thermally conductive material on which the heat dissipation fin 25 is mounted and which is provided with a lead part 21 connected with the lead out positions (foot print parts 13) of the heat dissipation path.