Investigation of compositional and structural modifications induced by heat treatment of pulsed laser deposited amorphous CNx(x similar to 0.23) thin film has been carried out. Fourier transform infrared, Raman scattering, X-ray photoelectron spectroscopies were carried out to investigate compositional and structural properties of films. The heat treatment induces a nitrogen loss of the him. The N/C ratio decreased from 0.23 for the as-deposited film to 0.17 for the film heat treated at 800 degreesC. N1s electron spectra showed nitrogen atoms bonded to sp(3) hybridized carbon preferentially removed by heat treatment, although those bonded to sp(2) hybridized carbon were stable. Simultaneously, growth of graphitic domains, i.e. graphitization of the film by heat treatment was observed by Raman spectroscopy. The nitrogen loss and changes in bonding structure concerned with nitrogen atoms by heat treatment are caused by the graphitization of amorphous CNx film induced by heat treatment.