To more activate an alloy powder without largely eluting electrochemically active essential components such as Mn by dipping the alloy powder into an acidic aq. soln. of copper salt having pH within a specified range, and then dipping it into an alkaline aq. soln.

The hydrogen storage alloy powder is dipped into an acidic aq. soln. of pH <7 contg. copper salt and is subjected to surface treatment at a room temp. In this way, Mn segregated phases in the surface layer of the hydrogen storage alloy is preferentially applied with substitution plating with copper salt under uneven distribution to newly form copper metallic components in the Mn phases. Next, the hydrogen storage alloy powder is dippted into an alkaline aq. soln., and rare metal elements in the alloy surface easy to dissolve in alkali are eluted to relatively increase the concn. of nickel in the alloy surface. As the copper salt, an aq. soln. of 0.1 to 10 wt.% concn. as copper ions at a room temp., particularly, of cupric sulfate and cupric chloride can suitably be used. The dipping treatment with an alkaline aq. soln. is executed preferably at 20 to 100°C.