PURPOSE: To keep quality of a heating member and improve a reliability in operation of the heating member by a method wherein a generated heat of the heating member is efficiently radiated to prevent a thermal trouble of the heating member.

CONSTITUTION: Semiconductor element 1 acting as heat generating members are arranged side by side in a longitudinal direction on one surface of a main heat receiving member 2, and radiation fins 4 are arranged on the other surface and vertically installed. Sub-heat receiving members 3 are provided with radiation fins 4 in a longitudinal direction on one surface in a thickness direction and they are vertically installed. The two members of the main heat receiving member 2 and the sub-heat receiving member 3 are arranged side by side in a thickness direction in such a manner that each of the radiation fins 4 is positioned on the right side of each of the sub-heat receiving members 3. U-shaped bent heat pipes 5, 6 are arranged such that their both legs of the U-shape may pass through each of the main heat receiving member 2 and the sub-heat receiving member 3 in a longitudinal direction between the main heat receiving member 2 and each of the sub-heat receiving member 3. It is possible to additionally provide a set of the sub-heat receiving members 3 and the radiation fins 4 in response to the degree of air-cooling for the semiconductor elements 1.