Recently, there has been a growing demand for soft magnetic materials with high conversion characteristics in the high-frequency range due to the trend where electric devices are being operated at higher frequencies. P/M soft magnetic materials, which were developed for such devices, utilizing iron-based powder and alloy powder. Through this work, we were able to reduce core loss and achieve remarkable magnetic characteristics in the high frequency range. Core loss, which includes hysteresis loss and eddy-current loss, is predominant in the high-frequency range. Two methods can be used to reduce eddy-current loss: using fine-grained powder, and using high-resistivity powder. However, both these present compressibility problems, with high-resistivity iron-based alloy powders such as Fe-Si being particularly poor in deformability. By studying composition of the material, we successfully developed a material that offers both high resistivity and high compressibility, reduction of core loss by more than 20% over the conventional material was achieved.