A surface treatment method for a hydrogen absorbing alloy powder of the present disclosure is used for a surface treatment on a hydrogen absorbing alloy powder containing rare earth elements and nickel as constituent elements, including an immersion process in which the hydrogen absorbing alloy powder is immersed in an aqueous alkaline solution; and a removal process in which a liquid containing the hydrogen absorbing alloy powder immersed in the aqueous alkaline solution is introduced into a liquid cyclone, and undesired substances having a smaller specific gravity than the hydrogen absorbing alloy powder adhered to the surface of the hydrogen absorbing alloy powder are removed.