A rectangular heating section is so shaped as to touch the electronic component except corners of the rectangle when the surface of the electronic component does not parallel the heating section. For example, the heating section is formed to be smaller than the electronic component surface, to be a rectangle which is smaller than the electronic component surface and comprises rounded corners, to be an octagon which is smaller than the electronic component surface and is formed by cutting off corners of the rectangle, or to be an octagon which is larger than the electronic component surface and is formed by cutting off corners of the rectangle. A die is prevented from being damaged due to a contact with the heating section of a cooling module at a given point of the die according to a mounting error or a usage state.