To provide a cooling device utilizing radiation cooling wherein a solid alumina material having high emissivity in the infrared range is brought into contact with the core or the package of a semiconductor integrated circuit with relatively high driving electric power such as a compact CPU or ASIC serving as a kernel to enhance or maintain performance in compact equipment via a metal plate for heat transfer which has high thermal conductivity such as, for example, an aluminum plate and a copper plate to convert thermal energy into infrared light and then emit it.

The cooling device includes the metal plate for heat transfer mounted on the top surface of the core or package of the semiconductor integrated circuit, and an alumina plate further mounted on the metal plate for heat transfer and composed principally of the alumina material of ≥0.8 in emissivity for radiation cooling, the area of the heat transfer plate and the area of the alumina plate being larger than that of the top surface of the core or package.