A soft magnetic alloy powder containing Fe--Ni-based crystal particles is provided as one capable of adequately reducing core loss of a powder magnetic core and achieving satisfactory magnetic characteristics at an effective operating temperature of an element. The present invention provides a soft magnetic alloy powder containing Fe--Ni-based crystal particles containing 45 to 55 mass % Fe and 45 to 55 mass % Ni, relative to a total mass of Fe and Ni, and containing 1 to 12 mass % Co and 1.2 to 6.5 mass % Si, relative to a total mass of Fe, Ni, Co, and Si.