The Co-33Cr-5Mo alloy powders containing nitrogen were prepared by gas atomization and water-atomization process, and selective laser melting process was performed using both the powders. Nitrogen content in the Co-Cr-Mo powders, which control the phase constitution of Co-Cr-Mo alloys, were almost the same. On the other hand, the oxygen content of the water-atomized powders were higher than that of the gas-atomized powders. SEM observation revealed that the oxide layer containing Cr and Si was formed on the surface, although the clean surface was observed for the gas-atomized powder. It should be noted that the porosity of the PBFL build using the gas-atomized powder was higher than that using the water-atomized powder, especially in the case of lower energy density. The porosity difference caused the mechanical properties difference at the lower energy density.