The magnetic properties of fcc Fe films grown on fcc Co(100) have been studied by means of spin-resolved Fe 3s core-level photoemission and characteristics of the measured spin-resolved 3s spectra for fcc Fe films have been investigated. The spin-resolved 3s spectra measured on 3.9 and 6.6 monolayer (ML) fcc Fe films are similar in spectral shape. The 3s majority-spin spectra for these fcc Fe films show weaker intensity on the high-binding-energy side than the spectrum previously reported for bulk bcc Fe. The spin-resolved 3s spectra for the fcc Fe films are analyzed by cluster model calculation consisting of four Fe atoms. In the analysis by the cluster model calculation, effects of the interatomic configuration interaction on the spin-resolved 3s spectra for fcc Fe films are discussed. Itinerancy of 3d electrons is found to be an important factor in describing the spin-resolved Fe 3s spectra. The z spin momentum estimated by the cluster calculation indicates that both the Fe films are in a high-spin ferromagnetic state near the surface. On the other hand, the spin polarization at the background in the spectrum for the 6.6 ML Fe film is much smaller than that for the 3.9 ML film. This variation of the background spin polarization indicates that the magnetic moment averaged up to deeper layers of Fe film is suppressed in the 6.6 ML film.