A heat dissipation device (1) has an insulation board (3) one side of which is a heat producing body mounting surface, and also has a heat sink (5) fixed to the other side of the insulation board (3). A metal layer (7) is provided on the surface opposite the heat producing body mounting surface of the insulation board (3). A stress relaxing member (4) is interposed between the metal layer (7) of the insulation board (3) and the heat sink (5). The stress relaxing member (4) is made of a material with high heat conductivity and is constructed from a plate-like body (10) and projections (11) spacedly formed on one side of the plate-like body (10). The top surfaces of the heads of the projections (11) of the stress relaxing member (4) are brazed to the metal layer (7), and that side of the plate-like body (10) on which the projections (11) are not formed is brazed to the heat sink (5). The heat dissipation device (1) has a reduced material cost and has excellent heat dissipation performance.