Provided herein is a dust core having high mechanical strength and high magnetic permeability. An alloy powder constituting the dust core is also provided. A soft magnetic powder is used that has a plurality of protrusions of 0.1 μm or more and 5 μm or less on an alloy powder surface. A dust core is used that contains at least 80 weight % of the soft magnetic alloy powder. A method for producing a soft magnetic powder is used that includes producing an amorphous soft magnetic alloy ribbon by liquid quenching; and pulverizing the amorphous soft magnetic alloy ribbon into a powder having a thickness of 0.1 μm or more and 40 μm or less without heat treatment. The pulverization cleaves the amorphous soft magnetic alloy ribbon, and produces a protrusion on a powder surface.