An XPS study of anodic oxidized glass-like carbon (GC) was conducted in order to investigate the inconsistency between O-1s/C-1s and oxygen concentration (Ocal.) calculated from the curve fitting results of the C-1s spectrum. Consideration of the asymmetric peak shape of the C-1s spectrum is normally done in order to obtain precise curve fitting results. However, it was found that the 2nd-carbon peak should also be taken into consideration in the curve fitting process in addition to the effect of asymmetric peak shape of carbon to obtain a consistent value of O-1s/C-1s. The 2nd graphitic peak is normally located +0.7-+0.8 eV away from the original C-1s spectrum. The ratio of the 2nd graphitic peak area in the C-1s spectrum increased as the electrical charge increased. However, the peak shapes of C-1s spectra of anodic oxidized GC after heat treatment at 1500 degrees C in argon atmosphere were almost the same as the C-1s of untreated GC. Although the origin of the 2nd graphitic peak is not well understood, it may be related to the amount of oxygen on the GC surface.