To provide a method for hardening the surface of an aluminum material or an alloy material thereof by which a hardened layer having excellent abrasive wear resistance, adhesive wear resistance and plastic deformation resistance.

The surface to be hardened in an aluminum(Al) material 1 whose surface is to be hardened is provided with a groove 2. This groove is filled with a build-up welding material 3, and as this build-up welding material 3, the one obtd. by filling an aluminum pipe 4, e.g. with the one obtd. by applying 30vol% Ni plating to NbC powder material as an adhesion resistant material is used. This material is charged to the inside of an electron beam welding machine, and the part of the build-up welding material 3 is irradiated with an electron beam. The part of the build-up welding material 3 is heated to melt by the irradiation of the electron beam, by which a build-up welding alloy in which the adhesive wear resistant material is largely and uniformly dispersed in the matrix alloy in which intermetallic compounds of Ni and aluminum used for the plating and aluminum are present can be formed.