Inverse photoemission spectrum calculation has been performed for Co/Cu(100) and Cu/Co(100) surfaces. We found that no quantum well states are reproduced computationally for Cu/Co(100), although we find quantum well states peaks in the calculated spectra for Co/Cu(100). The result of the paper suggests us that the mechanism of ''quantum well states like'' peaks in the inverse photoemission spectrum for Cu/Co(100) would be different from that of Co/Cu(100). Ar least, we found that the quantum well state theory cannot be applied to Cu/Co(100) surface.