Thermodynamic analysis has been carried out for growth of transition-metal nitride thin films by pulsed laser deposition. TiNfilms with (200) orientation were grown on Si(100) substrate without any oxide impurity phase formation at substratetemperature in the range of 20~700 oC. However, polycrystalline ZrN films mixed with ZrO2 phase were grown at 550~700 oCat the same deposition conditions. We prepared the diagram of chemical potential of nitrogen (μN2) with variation oftemperature for the nitride films and the PO2-PN2 phase diagram for Ti and Zr at 973 K. We could expect from thethermodynamic diagram that ZrO2 phase tends to be more easily formed at 700 oC than TiO2 phase during the nitride filmgrowth at the same gas atmosphere, as is consistent with experimental results. Formation and phase stability of TiN and ZrNfilms at elevated temperatures are systematically analyzed and compared to each other.