PURPOSE: To reduce the size and thickness and cost of a heat sink and enhance its cooling efficiency of a heat sink which cools the heat generated by internal loss of a power semiconductor.

CONSTITUTION: A first structural body A with a base board 1 and a blade section molded in one piece and a second structural body B with a base board section 4 and the blade section molded in once piece are installed where the board sections are laid out in parallel to each other. One end of a heat pipe 3 is connected to the base board section 1 of the first structural body A while the other end of the heat pipe is connected to the base board section 4 of the second structural body B. This construction makes it possible to attain the object of this invention and reduce the size of a power converter and enhance its reliability to a satisfactory extent.