In recent years, with increasing of a demand of alloyed steel powder, knowledge of gas release behavior has been required to improve the quality of the produced material. In this paper, the gas release behavior from Fe powder, Fe-Cr powder, Fe-Ni powder, and Fe-Cr-Ni powder during heating in pure He gas were investigated by a gas chromatography analyzer. CO2, H2O, and C3H8 gases were detected from the powders. Especially, in Fe powder and Fe-Ni powder, CO2 gas was remarkably released over 600°C. H2O gas generation was detected from Fe-Ni powder and Fe-Cr-Ni powder in temperature range of 200-600°C. The amount of CO2 gas in Fe powder and Fe-Ni powder was clearly higher than that in Fe-Cr powder and Fe-Cr-Ni powder. Additionally, the amount of H2O gas in Fe-Ni powder and Fe-Cr-Ni powder was also higher than that in Fe powder and Fe-Cr powder. Precisely, it was guessed that CO2 gas release behavior depended on the Cr component in the alloyed steel powder, and that H2O gas release behavior rerated with Ni component. As comparative experiments, the gas release behavior of pure Cr powder, pure Ni powder, and NiO powder were studied. Furthermore, for the alloyed steel powder mixed with carbon powder, and for the alloyed steel powder treated in steam vapor, the amount of gas release were measured. From these investigations, the effects of Cr and Ni components against the gas release behavior of the alloyed steel powder were discussed in this paper.