We present here the changes in the valence band and the C 1score peak and its shake-up satellite of a C60film upon photopolymerization using x-ray photoelectron spectroscopy. It was found that the intensity of the C 1sshake-up satellite of the phototransformed C60film decreased with increasing irradiation time of 500 W mercury lamp (0 to 200 h). On the other hand, the valence band spectra of the C60film was almost unchanged even after 200 h of irradiation, compared with that of pristine C60film.