A cooling device of a multi-chip module has micropackages that are independent of thermal deformation and easy to assembly and disassembly. The multi-chip module includes a multi-layer substrate on which the micropackages, each encasing an LSI chip, are mounted, and a housing formed integrally with a cooler. Each of the micropackages includes a first heat conduction member, having a cap portion for receiving the LSI chip and a first fin made of the same material as the cap portion to be integral therewith, and a substrate fixed to the cap portion of the first heat conduction member, the LSI chip being mounted on the substrate which is securely fixed to the cap portion of the heat conduction member while being fixedly joined at the back surface thereof to an inner surface of the cap portion of the first heat conduction member. Second heat conduction members, each including a base portion and a second fin, are disposed to engage with the first fins and be pressed against the cooler by a spring, respectively.