Alloy particles of an alloy having a face-centered cubic structure comprise at least one selected from Fe and Co and at least one selected from Pt and Pd as principal components. The alloy particles have a TEM-measured average grain size (D.sub.TEM) of not more than 50 nm, and a single crystallinity (D.sub.TEM)/(D.sub.X) that is less than 1.50, where (D.sub.X) is X-ray crystallite size. These alloy particles can be advantageously manufactured by using the polyol process to synthesize the alloy particles in the presence of a complexing agent.