To provide iron-nickel alloy powder which has a grain size smaller than that of metal powder by the conventional technique at a low cost and also has high saturation magnetic flux density, and to provide a powder magnetic core for an inductor using the iron-nickel alloy powder.

The iron-nickel alloy powder which has the grain size smaller than that of metal powder by the conventional technique and also has high saturation magnetic flux density by using the mixture of an iron-containing inorganic acid salt or organic acid salt with a nickel-containing inorganic acid salt or organic acid salt as the starting raw material and performing hydrogen reduction treatment in a hydrogen current in a temperature range lower than that in the conventional technique. Further, using the iron-nickel alloy powder, by controlling the content of a binder to the ratio of 1 to 5 wt.%, the powder magnetic core for the inductor which has saturation magnetic flux density higher than that of the powder magnetic core for the inductor by the conventional technique, and has low loss and high efficiency can be obtained.