PURPOSE: To lessen the work of attaching a heat sink in man-hours and to simplify the work of attaching the heat sink by a method wherein a cutout to which a hook is fastened is provided to both the sides of package main body.

CONSTITUTION: A cutout 4 provided with two cutout faces 4a vertical to each other is provided to a resin section 2. An elastically deformable heat sink 5 is composed of a U-shaped base 7 provided hooks 6 at both its ends and a large number of heat dissipating fins 8 connected to the base 7. The heat sink 5 is fitted to the resin section 2 of a package main body 1 by fastening the hooks 6 to the cutouts 4. In an IC package constituted as above, the heat sink 5 can be attached to the package main body 1 by fastening the hooks 6 to the cutouts 4 elastically deforming the heat sink 5 itself.