Abstract: The present invention relates to a cooling unit for electronic devices wherein the manufacturing method comprises the steps of: (a) preparing a plate-type metal block for removing heat generated from an electronic component, the metal block having holes in the thickness part of the metal block and having convex portions formed on one main surface or both main surfaces of the metal block; (b) inserting heat pipes into the holes; and (c) applying a local and two-dimensional force from the surface of the metal block to the convex portions to make the surface flat bringing the outer surface of each heat pipe into close contact with the inner wall of each hole in the metal block.