In a method for producing a hydrogen generating material including at least one metal powder selected from the group consisting of an aluminum powder and an aluminum alloy powder of the present invention, a metal flake powder is formed by pulverizing aluminum or aluminum alloy mechanically in a treatment solvent containing an organic solvent that is corrosive to aluminum. The hydrogen generating material of the present invention includes, e.g., at least one metal powder selected from the group consisting of an aluminum powder and an aluminum alloy powder. The metal powder is in the form of a flake and includes 60 wt % or more of aluminum in the metallic state. The carbon content of the metal powder measured by a combustion-infrared absorption method is 0.5 wt % or less.