Provided is iron-based metal powder for powder metallurgy including a metallic soap containing at least one or more types selected from a group of Ag, Au, Bi, Co, Cu, Mo, Ni, Pd, Pt, Sn, Te and W having a higher standard oxidization potential than iron, and an iron sintered body having a rust prevention function, wherein at least one or more types of metallic soap selected from a group of Ag, Au, Bi, Co, Cu, Mo, Ni, Pd, Pt, Sn, Te and W having a higher standard oxidization potential than iron is added to iron-based metal powder for powder metallurgy, and sintering is performed thereto. As a result, obtained is mixed powder for powder metallurgy capable of improving the rust prevention effect easily without having to hardly change the conventional processes.