To provide a heat spreader 1 which has a substrate 2 made of an aluminum-ceramic composite material with the outer peripheral surface thereof coated with a coating layer 9 having a high heat conductivity and an excellent bond strength with a small and uniform thickness, which has a small total heat expansion in the surface direction, and which has an excellent total heat conductivity in the thickness direction, and to provide a manufacturing method of the same.

In a heat spreader 1, the purity of aluminum in an aluminum-ceramic composite material is 99 mass% or more; a thickness of a coating layer 9 constituting an element mounting surface 10 is 0.05 to 0.5 mm; a magnesium content in an aluminum-magnesium alloy forming the coating layer 9 is 0.4 to 8.5 mass%; and a bond strength between a substrate 2 and the coating layer 9 is 100 MPa or more. In the manufacturing method of the same, a non-oxidizing or reductive heating gas is introduced into an aluminum die cast metallic mold to heat the substrate, and then the aluminum-magnesium alloy is pressed into the aluminum die cast metallic mold which is in a sealed state.