An alloy steel powder for powder metallurgy includes an iron-based powder containing about 0.5 mass percent or less of Mn as a prealloyed element and 0.2 to about 1.5 mass percent of Mo as a prealloyed element; and a Mo-containing alloy powder bonded on the surface of the iron-based powder by diffusion bonding. In the alloy steel powder for powder metallurgy, a Mo average content [MO]T (mass percent) satisfies formula 0.8≧[M]T—[Mo]P≧0.05, wherein the content [Mo]P is the above prealloyed Mo content (mass percent) in the iron-based powder.