To provide a method for manufacturing a heat spreader, capable of manufacturing a heat spreader in such a manner that the inner wall of a recessed part is not formed taper-shaped and an X-shaped figure will not be generated on the bottom face.

The method comprises a pressing step and a cutting step. In the pressing step, by using an upper mold 40 having a punch 42 and a holding part 44, which is formed around the punch 42 for holding a plate 31 at the peripheral parts 34 around a recessed part 32, and a lower mold 50 on which the plate 31 is placed, with the holding part 44 closing the mold to hold the plate 31 prior to pressing on the plate 31 by the punch 42; and then the recessed part 32 is formed with the punch 42, by closing the mold by the punch 42 and the lower mold 50, and pressing is carried out so that a flowing material 33 protrudes from the outer wall part of the plate 31; when the recessed part 32 is formed by the punch 42. In the cutting step, the flowing material 33 formed during the pressing step is cut.