A heat radiator 1 includes an insulating substrate 3 whose first side serves as a heat-generating-element-mounting side, and a heat sink 5 fixed to a second side of the insulating substrate 3. A metal layer 7 is formed on the second side of the insulating substrate 3 opposite the heat-generating-element-mounting side. A stress relaxation member 4 formed of a high-thermal-conduction material intervenes between the metal layer 7 of the insulating substrate 3 and the heat sink 5 and includes a plate-like body 10 and a plurality of projections 11 formed at intervals on one side of the plate-like body 10. The end faces of the projections 11 of the stress relaxation member 4 are brazed to the metal layer 7, whereas the side of the plate-like body 10 on which the projections 11 are not formed is brazed to the heat sink 5. This heat radiator 1 is low in material cost and exhibits excellent heat radiation performance.