Hydrogenated amorphous carbon (a–C:H) films on stainless steel (AISI430) substrate oxidized in air at 1273 K were prepared from a gas mixture of methane and hydrogen by an rf plasma chemical vapor deposition, and thermally stimulated exoelectron emission (TSEE) was studied for the x-ray irradiated a–C:H films. Glow curves and energy distributions of TSEE from the 80- and 280-nm a–C:H films and from the AISI430 substrate have been measured under ultrahigh vacuum conditions. It was found that the glow curve from the 80-nm a–C:H film was similar to that from the AISI430 substrate, but it was quite different from that from the 280-nm film; the values of the mean energy of exoelectrons at the glow peak temperatures from the 80-nm a–C:H film are almost the same as those from the substrate but are much lower than those of the 280-nm film. The surfaces of 80- and 280-nm a–C:H films are observed with the scanning electron microscope (SEM). Observations by SEM show that the 80-nm film has relatively large-sized clusters of films and the stainless steel substrate still appears in some places, but the surface of the 280-nm film is completely covered by the carbon films. From these results, we propose that TSEE from the 80-nm film originates mainly from the oxide films on the stainless steel substrate and TSEE from the 280-nm film originates from the film itself. Thus, TSEE can be applied to characterize the surface of thin films.