The present invention includes the following steps: setting the thickness of an interposer to an initial value; determining the axial force of the interposer and the radius of curvature of the warpage caused by the difference in the thermal expansion coefficients of the supporting substrate, the joined layer and the interposer at the set thickness; determining the absolute value of the stress on the chip-connecting surface of the interposer from the stress due to the axial force of the interposer and the stress due to the warpage using the determined axial force and the radius of curvature; determining whether or not the absolute value of the stress is within a tolerance; changing the thickness of the interposer by a predetermined value; and confirming the set thickness as the thickness of the interposer when the determined absolute value of the stress is within the tolerance.