Abstract: A memory module 10 is fitted with a “cover and heat sink” 5 having a U-shape in cross section in such a manner that the memory module 10 is inserted into a U-shaped deep recess of the “cover and heat sink” 5, and all packaged memory ICs 3 and the other components 2 mounted on each face of a printed circuit board 1 are covered by the “cover and heat sink” 5, with a silicone grease 6 being filled between the “cover and heat sink” 5 and the packaged memory ICs 3. The heat generated in each packaged memory IC 3 is conducted to the “cover and heat sink” 5 through the silicone grease 6, and the heat is radiated from the surface of the “cover and heat sink” 5 having a large surface area. In addition, since all the components 2 and 3 mounted on the printed circuit board 1 are covered with the “cover and heat sink” 5, the components 2 and 3 mounted on the printed circuit board 1 are protected from a mechanical shock.